Electrochromic devices

ABSTRACT

Conventional electrochromic devices frequently suffer from poor reliability and poor performance. Improvements are made using entirely solid and inorganic materials. Electrochromic devices are fabricated by forming an ion conducting electronically-insulating interfacial region that serves as an IC layer. In some methods, the interfacial region is formed after formation of an electrochromic and a counter electrode layer. The interfacial region contains an ion conducting electronically-insulating material along with components of the electrochromic and/or the counter electrode layer. Materials and microstructure of the electrochromic devices provide improvements in performance and reliability over conventional devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part of U.S. patent applicationSer. No. 12/772,055, filed Apr. 30, 2010, entitled “ElectrochromicDevices”, U.S. patent application Ser. No. 12/814,277, filed Jun. 11,2010, entitled “Electrochromic Devices”, and U.S. patent applicationSer. No. 12/814,279, filed Jun. 11, 2010, entitled “ElectrochromicDevices”, each of which is incorporated herein by reference in itsentirety and for all purposes.

FIELD

This disclosure relates to electrochromic devices, methods offabrication, associated apparatus and the like.

BACKGROUND

Electrochromism is a phenomenon in which a material exhibits areversible electrochemically-mediated change in an optical property whenplaced in a different electronic state, typically by being subjected toa voltage change. The optical property is typically one or more ofcolor, transmittance, absorbance, and reflectance. One well knownelectrochromic material, for example, is tungsten oxide (WO₃). Tungstenoxide is a cathodic electrochromic material in which a colorationtransition, transparent to blue, occurs by electrochemical reduction.

Electrochromic materials may be incorporated into, for example, windowsand mirrors. The color, transmittance, absorbance, and/or reflectance ofsuch windows and mirrors may be changed by inducing a change in theelectrochromic material. One well known application of electrochromicmaterials, for example, is the rear view mirror in some cars. In theseelectrochromic rear view mirrors, the reflectivity of the mirror changesat night so that the headlights of other vehicles are not distracting tothe driver.

While electrochromism was discovered in the 1960's, electrochromicdevices still unfortunately suffer various problems and have not begunto realize their full commercial potential. Advancements inelectrochromic technology, apparatus and related methods of makingand/or using them, are needed.

SUMMARY

A typical electrochromic device includes an electrochromic (“EC”)electrode layer and a counter electrode (“CE”) layer, separated by anionically conductive (“IC”) layer that is highly conductive to ions andhighly resistive to electrons. In other words, the ionically conductivelayer permits transport of ions but blocks electronic current. Asconventionally understood, the ionically conductive layer thereforeprevents shorting between the electrochromic layer and the counterelectrode layer. The ionically conductive layer allows theelectrochromic and counter electrodes to hold a charge and therebymaintain their bleached or colored states. In conventionalelectrochromic devices, the components form a stack with the ionconducting layer sandwiched between the electrochromic electrode and thecounter electrode. The boundaries between these three stack componentsare defined by abrupt changes in composition and/or microstructure.Thus, the devices have three distinct layers with two abrupt interfaces.

Quite surprisingly, the inventors have discovered that high qualityelectrochromic devices can be fabricated without depositing anionically-conducting electronically-insulating layer. In accordance withcertain embodiments, the counter electrode and electrochromic electrodesare formed immediately adjacent one another, often in direct contact,without separately depositing an ionically-conducting layer. It isbelieved that various fabrication processes and/or physical or chemicalmechanisms produce an interfacial region between contactingelectrochromic and counter electrode layers, and this interfacial regionserves at least some functions of an ionically conductiveelectronically-insulating layer in conventional devices. Certainmechanisms that may be key to forming the interfacial region aredescribed below.

The interfacial region typically, though not necessarily, has aheterogeneous structure that includes at least two discrete componentsrepresented by different phases and/or compositions. Further, theinterfacial region may include a gradient in these two or more discretecomponents. The gradient may provide, for example, a variablecomposition, microstructure, resistivity, dopant concentration (forexample, oxygen concentration), and/or stoichiometry.

In addition to the above discoveries, the inventors have observed thatin order to improve device reliability, two layers of an electrochromicdevice, the electrochromic (EC) layer and the counter electrode (CE)layer, can each be fabricated to include defined amounts of lithium.Additionally, careful choice of materials and morphology and/ormicrostructure of some components of the electrochromic device provideimprovements in performance and reliability. In some embodiments, alllayers of the device are entirely solid and inorganic.

Consistent with above observations and discoveries, the inventors havediscovered that formation of the EC-IC-CE stack need not be done in theconventional sequence, EC→IC→CE or CE→IC→EC, but rather an ionconducting electronically-insulating region, serving as an IC layer, canbe formed after formation of the electrochromic layer and the counterelectrode layer. That is, the EC-CE (or CE-EC) stack is formed first,then an interfacial region serving some purposes of an IC layer isformed between the EC and CE layers using components of one or both ofthe EC and CE layers at the interface of the layers. Methods describedherein not only reduce fabrication complexity and expense by eliminatingone or more process steps, but provide devices showing improvedperformance characteristics.

Thus, one embodiment is a method of fabricating an electrochromicdevice, the method including: forming an electrochromic layer includingan electrochromic material; forming a counter electrode layer in contactwith the electrochromic layer without first providing an ion conductingelectronically-insulating layer between the electrochromic layer and thecounter electrode layer; and forming an interfacial region between theelectrochromic layer and the counter electrode layer, where theinterfacial region is substantially ion conducting and substantiallyelectronically-insulating. The electrochromic layer and counterelectrode layer are typically, but not necessarily, made of one or morematerials more electronically conductive than the interfacial region butmay have some electronically resistive character. The interfacial regioncan contain component materials of the EC layer and/or the CE layer, andin some embodiments, the EC and CE layers contain component materials ofthe interfacial region. In one embodiment, the electrochromic layerincludes WO₃. In some embodiments, the EC layer includes WO₃, the CElayer includes nickel tungsten oxide (NiWO), and the IC layer includeslithium tungstate (Li₂WO₄).

Heating may be applied during deposition of at least a portion of theelectrochromic layer. In one embodiment, where the EC layer includesWO₃, heating is applied after each of a series of depositions viasputtering in order to form an EC layer with a substantiallypolycrystalline microstructure. In one embodiment, the electrochromiclayer is between about 300 nm and about 600 nm thick, but the thicknessmay vary depending upon the desired outcome which contemplates formationof the interfacial region after deposition of the EC-CE stack. In someembodiments, the WO₃ is substantially polycrystalline. In someembodiments, an oxygen rich layer of WO₃ can be used as a precursor tothe interfacial region. In other embodiments the WO₃ layer is a gradedlayer with varying concentrations of oxygen in the layer. In someembodiments, lithium is a preferred ion species for driving theelectrochromic transitions, and stack or layer lithiation protocols aredescribed. Specifics of the formation parameters and layercharacteristics are described in more detail below.

Another embodiment is a method of fabricating an electrochromic device,the method including: (a) forming either an electrochromic layerincluding an electrochromic material or a counter electrode layerincluding a counter electrode material; (b) forming an intermediatelayer over the electrochromic layer or the counter electrode layer,where the intermediate layer includes an oxygen rich form of at leastone of the electrochromic material, the counter electrode material andan additional material, where the additional material includes distinctelectrochromic and/or counter electrode material, the intermediate layernot substantially electronically-insulating; (c) forming the other ofthe electrochromic layer and the counter electrode layer; and (d)allowing at least a portion of the intermediate layer to becomesubstantially electronically-insulating and substantially ionconducting. Specifics of the formation parameters and layercharacteristics for this method are also described in more detail below.

In other embodiments, a substantially electronically-insulating and ionconducting region is formed on, and after formation of, theelectrochromic or the counter electrode layer, as a result of heating asuperstoichiometric oxygen form of the electrochromic or the counterelectrode layer in the presence of lithium. The other of theelectrochromic or the counter electrode layer is formed after, and on,the substantially electronically-insulating and ion conducting regionthus formed. In one example, the electrochromic layer is formed first,for example on a glass substrate having a transparent conductive oxidethereon. The electrochromic layer can have a first sub-layer of a metaloxide that is stoichiometric or sub-stoichiometric in oxygen and a toplayer that is superstoichiometric in oxygen, or the electrochromic layercan be a graded composition with at least a superstoichiometric upperportion. Superstoichiometric metal oxides are exposed to lithium andheated to form the substantially electronically-insulating and ionconducting region. The counter electrode is formed thereon as part offabrication of a functioning electrochromic stack. Further details ofthese methods are described below.

In other embodiments, a substantially electronically-insulating and ionconducting interfacial region is formed after formation of theelectrochromic or the counter electrode layer, as a result of exposing asuperstoichiometric oxygen form of the electrochromic or the counterelectrode layer to lithium, followed by formation of the other of theelectrochromic or the counter electrode layer. That is, during formationof the second electrode, a lithium flux is driven from the first formedelectrode layer (having been exposed to lithium) into the second formed,or forming, electrode layer. It is believed that this lithium flux maydrive formation of the substantially electronically-insulating and ionconducting interfacial region. In one example, the electrochromic layeris formed first, for example on a glass substrate having a transparentconductive oxide thereon. The electrochromic layer can have a firstsub-layer of a metal oxide that is stoichiometric or sub-stoichiometricin oxygen and a top layer that is superstoichiometric in oxygen, or theelectrochromic layer can be a graded composition with at least asuperstoichiometric upper portion. Superstoichiometric metal oxides areexposed to lithium, for example sputtering lithium. The counterelectrode is formed thereon where the aforementioned lithium flux formsthe substantially electronically-insulating and ion conductinginterfacial region between the electrochromic and counterelectrodelayers. Further details of these methods are described below.

Another embodiment is an apparatus for fabricating an electrochromicdevice, including: an integrated deposition system including: (i) afirst deposition station containing a material source configured todeposit an electrochromic layer including an electrochromic material;and (ii) a second deposition station configured to deposit a counterelectrode layer including a counter electrode material; and a controllercontaining program instructions for passing the substrate through thefirst and second deposition stations in a manner that sequentiallydeposits a stack on the substrate, the stack having an intermediatelayer sandwiched in between the electrochromic layer and the counterelectrode layer; where either or both of the first deposition stationand the second deposition station are also configured to deposit theintermediate layer over the electrochromic layer or the counterelectrode layer, and where the intermediate layer includes an oxygenrich form of the electrochromic material or the counter electrodematerial and where the first and second deposition stations areinterconnected in series and operable to pass a substrate from onestation to the next without exposing the substrate to an externalenvironment. In one embodiment, apparatus are operable to pass thesubstrate from one station to the next without breaking vacuum and mayinclude one or more lithiation stations operable to deposit lithium froma lithium-containing material source on one or more layers of theelectrochromic device. In one embodiment, apparatus are operable todeposit the electrochromic stack on an architectural glass substrate.Apparatus need not have a separate target for fabrication of an ionconducting layer.

Another embodiment is an electrochromic device including: (a) anelectrochromic layer including an electrochromic material; (b) a counterelectrode layer including a counter electrode material; and (c) aninterfacial region between the electrochromic layer and the counterelectrode layer, where the interfacial region includes anelectronically-insulating ion conducting material and at least one ofthe electrochromic material, the counter electrode material and anadditional material, where the additional material includes distinctelectrochromic and/or counter electrode material. In some embodimentsthe additional material is not included; in these embodiments theinterfacial region includes at least one of the electrochromic materialand the counter electrode material. Variations in the composition andmorphology and/or microstructure of the interfacial region are describedin more detail herein. Electrochromic devices described herein can beincorporated into windows, in one embodiment, architectural glass scalewindows.

Another embodiment is an EC element which is a single layer gradedcomposition including an EC region, an IC region and a CE region,respectively. In certain embodiments, the EC element is all solid-stateand inorganic. The EC element can be described in a number of ways, asdetailed below. The EC element functions as an EC device, but is asingle layer, not multiple layers, one stacked upon the other, as inconventional practice. In certain embodiments, the EC element includestransition metal oxides, alkali metals and mixed transition metaloxides. One embodiment is an EC device including a first transparentelectrode, a second transparent electrode, and the EC element sandwichedin between the first and second transparent electrodes. In oneembodiment, described in more detail in relation to FIG. 4G, an ECelement includes transparent conducting regions as well, i.e. a fullyfunctioning EC element that is a single coating on a substrate.

Another embodiment is a method of fabricating a single layer EC elementon a substrate in a sputter system, including: a) sputter coating an ECmaterial including a first transition metal and a first oxygenconcentration onto the substrate; b) increasing from the first oxygenconcentration to a second oxygen concentration, higher than the first,during a); c) introducing lithium into the sputter system; and, d)sputter coating a CE material including a second transition metal andoxygen; wherein the fabrication is a substantially continuous processand the concentration of the first transition metal is decreased from a)to d), and the concentration of the second transition metal is increasedfrom a) to d). In certain embodiments the first transition metal istungsten and the second transition metal is nickel. Lithium may beintroduced into the sputter system in a variety of ways includingsputtering, evaporation and the like.

Yet another embodiment is a method of fabricating a single layer ECelement on a substrate in a sputter system, including sputter coatingmaterials from a plurality of closely associated sputter targets suchthat there is mixing of materials sputtered from each target in theregion where two targets are proximate each other; wherein the singlelayer EC element is fabricated upon a single pass of the substrate andthe plurality of closely associated sputter targets past each other.

Another embodiment is a method of fabricating a single layer EC elementon a substrate in a sputter system, including sputter coating materialsfrom a single sputter target including a composition reflective of thesingle layer EC element; wherein the single layer EC element isfabricated upon a single pass of the substrate and the single sputtertarget past each other.

These and other features and advantages will be described in furtherdetail below, with reference to the associated drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description can be more fully understood whenconsidered in conjunction with the drawings in which:

FIG. 1A is a schematic cross-section depicting conventional formation ofan electrochromic device stack.

FIG. 1B is a graph showing composition of EC, IC and CE layers in aconventional electrochromic stack.

FIGS. 2A-F are graphs showing representative component compositions forelectro chromic devices.

FIGS. 3A and 3B are process flows in accord with embodiments describedherein.

FIGS. 4A-4D are schematic cross-sections depicting formation ofelectrochromic devices in accord with specific embodiments describedherein.

FIGS. 4E-4G depict sputter targets and aspects of sputtering methods inaccord with embodiments described herein.

FIG. 4H depicts a schematic cross section of an electrochromic element.

FIGS. 4I-4L depict sputter targets and aspects of sputtering methods inaccord with embodiments described herein.

FIGS. 4M, 4N, 4P and 4Q are schematic representations of sputteringaccording to embodiments described herein.

FIG. 5 depicts an integrated deposition system in a perspective view.

FIG. 6 is a graph showing how process parameters and endpoint readoutscorrelate during formation of an electrochromic stack in accord withembodiments described herein.

FIGS. 7 and 8A-C are actual cross-sections of electrochromic devicesmade using methods in accord with embodiments described herein.

DETAILED DESCRIPTION

FIG. 1A is a schematic cross-section depicting a conventionalelectrochromic device stack, 100. Electrochromic device 100 includes asubstrate 102, a conductive layer (CL) 104, an electrochromic (EC) layer106, an ion conducting (IC) layer 108, a counter electrode (CE) layer110, and a conductive layer (CL) 112. Elements 104, 106, 108, 110, and112 are collectively referred to as an electrochromic stack 114.Typically, the CL layers are made of a transparent conductive oxide, andare commonly referred to as “TCO” layers. Since the TCO layers aretransparent, the coloring behavior of the EC-IC-CE stack is observablethrough the TCO layers, for example, allowing use of such devices on awindow for reversible shading. A voltage source 116, operable to applyan electric potential across electrochromic stack 114, effects thetransition of the electrochromic device from, for example, a bleachedstate (i.e., transparent) to a colored state. The order of the layersmay be reversed with respect to the substrate. That is, the layers canbe in the following order: substrate, transparent conductive layer,counter electrode layer, ion conducting layer, electrochromic materiallayer and (another) transparent conductive layer.

Again referring to FIG. 1A, in conventional methods of fabricating anelectrochromic stack, the individual layers are deposited one atop theother in a sequential format as depicted in the schematic on the leftside of FIG. 1A. That is, TCO layer 104 is deposited on substrate 102.Then EC layer 106 is deposited on TCO 104. Then IC layer 108 isdeposited on EC layer 106, followed by deposition of CE layer 110 on IClayer 108, and finally TCO layer 112 on CE layer 110 to formelectrochromic device 100. Of course, the order of steps can be reversedto make an “inverted” stack, but the point is that in conventionalmethods the IC layer is necessarily deposited on the EC layer followedby deposition of the CE layer on the IC layer, or the IC layer isdeposited on the CE layer followed by deposition of the EC layer on theIC layer. The transitions between the layers of material in the stackare abrupt.

One notable challenge with above procedure is the processing required toform the IC layer. In some prior approaches it is formed by a sol gelprocess which is difficult to integrate into a CVD or PVD processemployed to form the EC and CE layers. Further, IC layers produced bysol gel and other liquid-based processes are prone to defects thatreduce the quality of the device and may need to be removed by, forexample, scribing. In other approaches, the IC layer is deposited by PVDfrom a ceramic target, which can be difficult to fabricate and use.

FIG. 1B is a graph depicting material % composition versus position inthe electrochromic stack of FIG. 1A, namely layers 106, 108 and 110,that is, the EC, IC and CE layers. As mentioned, in conventionalelectrochromic stacks, the transitions between the layers of material inthe stack are abrupt. For example, EC material 106 is deposited as adistinct layer with little or no compositional bleed over to theadjacent IC layer. Similarly, IC material 108 and CE material 110 arecompositionally distinct with little or no bleed over to adjacentlayers. Thus, the materials are substantially homogeneous (except forcertain compositions of CE material described below) with abruptinterfaces. Conventional wisdom was that each of the three layers shouldbe laid down as distinct, uniformly deposited and smooth layers to forma stack. The interface between each layer should be “clean” where thereis little intermixing of materials from each layer at the interface.

One of ordinary skill in the art would recognize that FIG. 1B is anidealized depiction, and that in a practical sense there is inevitablysome degree of material mixing at layer interfaces. The point is, inconventional fabrication methods any such mixing is unintentional andminimal. The inventors have found that interfacial regions serving as IClayers can be formed where the interfacial region includes significantquantities of one or more electrochromic and/or counter electrodematerials by design. This is a radical departure from conventionalfabrication methods. In certain embodiments, there are no distinctlayers as in conventional EC devices, that is, the conventional ECdevice is replaced with an EC element, that is, a single layer of gradedmaterials that serves the function of an EC device. Various methods offorming these novel constructs are described in more detail below.

For the purposes of this disclosure, an EC device is an electrochromicstack construct, i.e., having more than one layer. An EC element is asingle layer graded composition that serves the function of an ECdevice. It its most basic form, an EC element includes an EC region, anIC region and a CE region, in the form of a single layer gradedcomposition. Thus supplied with, e.g, appropriate ions and when a fieldis applied across it, an EC element would color or bleach as an ECdevice would. If such an EC element is sandwiched between two electrodelayers, then this would, collectively, constitute an EC device. However,if the EC element itself comprises not only EC, IC and CE regions, butalso, e.g., transparent electrode regions, then it is not an EC device,it is an EC element because it is a single layer graded compositionserving the function of an EC device. Certain embodiments describedherein relate to EC devices, where there are at least two distinctlayers in a stack format, while other embodiments relate to EC elementswhere there is only a single layer graded composition that serves thefunction of an EC device.

As mentioned above, the inventors have discovered that formation of theEC-IC-CE stack need not be conducted in the conventional sequence,EC→IC→CE or CE→IC→EC, but rather an interfacial region serving as theion conducting layer can be formed after deposition of theelectrochromic layer and the counter electrode layer. That is, the EC-CE(or CE-EC) stack is formed first, then an interfacial region, which maypossess at least some functions of an IC layer, is formed between the ECand CE layers using components of one or both of the layers (and oranother electrochromic or counter electrode material in someembodiments) at the interface of the layers. In some embodiments, the ECor CE is formed, including a superstoichiometric portion which mayinclude an upper layer, and then exposed to lithium and heat to form anionically-conducting substantially electronically-insulating region,followed by formation of the other of the EC and the CE. Theionically-conducting substantially electronically-insulating region thenserves as the interfacial region between the EC and CE. In otherembodiments, the EC or the CE is formed, including a superstoichiometricportion or upper layer, and then exposed to lithium, for example, viasputtering lithium. The other of the EC and CE is then formed thereon.It is believed that formation of the second electrode drives a lithiumflux from the first formed electrode toward the second electrode. Inturn, this flux of lithium drives formation of an ionically-conductingsubstantially electronically-insulating interfacial region between theEC and CE layers. In other embodiments a single layer gradedcomposition, an EC element, is fabricated. The EC element includes an ECregion, an IC region (the interfacial region) and a CE region (an ionstorage region that may or may not also be electrochromic). Theinterfacial region serves at least some function of a conventional IClayer because it is substantially ion conducting and substantiallyelectronically-insulating. It should be noted, however, that interfacialregions as described can have higher than conventionally acceptedleakage currents but the devices show good performance nonetheless.

In one embodiment the electrochromic layer is formed with an oxygen richregion which is converted to the interfacial region or layer serving asan IC layer upon subsequent processing after the counter electrode layeris deposited. In some embodiments, a distinct layer which includes anoxygen rich version of an electrochromic material is used to(ultimately) form an interfacial layer serving as an IC layer betweenthe EC and CE layers. In other embodiments, a distinct layer whichincludes an oxygen rich version of a counter electrode material is usedto (ultimately) form an interfacial region serving as an IC layerbetween the EC and CE layers. All or a portion of the oxygen rich CElayer is converted to the interfacial region. In yet other embodiments,a distinct layer which includes an oxygen rich version of a counterelectrode material and an oxygen rich form of an electrochromic materialis used to (ultimately) form an interfacial region serving as an IClayer between the EC and CE layers. In other words, some or all ofoxygen rich material serves as a precursor to the interfacial regionthat serves as an IC layer. Methods described herein can not only reduceprocess steps, but produce electrochromic devices showing improvedperformance characteristics.

As mentioned, it is believed that some of the EC and/or CE layer in aninterfacial region is converted to a material that provides one or morefunctions of an IC layer, notably high conductivity for ions and highresistivity for electrons. The IC functional material in the interfacialregion may be, for example, a salt of the conductive cations; forexample, a lithium salt.

FIGS. 2A, 2B and 2C show composition graphs of three possible examplesof electrochromic device stacks (each containing an EC layer, a CE layerand an interfacial region serving as an IC layer), where the EC materialis tungsten oxide (denoted here as WO₃, but meant to include WO_(K),where x is between about 2.7 and about 3.5, in one embodiment x isbetween about 2.7 and about 2.9), the CE material is nickel tungstenoxide (NiWO) and the interfacial region primarily comprises lithiumtungstate (denoted here as Li₂WO₄, in another embodiment, theinterfacial region is a nanocomposite of between about 0.5 and about 50(atomic) % Li₂O, between about 5 and about 95% Li₂WO₄, and about 5 andabout 70% WO₃) with some amount of the EC and/or the CE material. Inmore general terms, the interfacial region typically, though notnecessarily, has a heterogeneous structure that includes at least twodiscrete components represented by different phases and/or compositions,which phases or compositions vary in concentration over the width of theinterfacial region. Because of this the interfacial region that servesas an IC layer is sometimes referred to herein as a “gradient region,” a“heterogeneous IC layer” or a “dispersed IC layer.” The illustrations inFIGS. 2A, 2B and 2C, although described in terms of specific materials,are more generally representative of composition variations of anysuitable materials for electrochromic devices described herein.

FIG. 2A depicts an electrochromic stack where the EC material is asignificant component of the interfacial region that functions as an IClayer, while the CE material is not a significant component. Referringto FIG. 2A, starting at the origin and moving from left to right alongthe x-axis, one can see that a portion the EC material, WO₃, which issubstantially all tungsten oxide, serves as the EC layer. There is atransition into the interfacial region where there is gradually lesstungsten oxide and correspondingly gradually more of lithium tungstate,up to and including near the end of the interfacial region where thereis a portion that is substantially all lithium tungstate with some minoramounts of tungsten oxide. Although the transition from the EC layer tothe interfacial region is demarked at a composition of substantially alltungsten oxide and de minimus amounts of lithium tungstate, it is clearthat the transition is not abrupt as in conventional devices. In thisexample, effectively the transition begins to occur where thecomposition has sufficient quantity of lithium tungstate to enable thematerial to serve at least some functions of an IC layer, for example,ion conduction and electronic insulation. Certainly the composition muchcloser to the CE layer, where the composition is substantially lithiumtungstate, serves the function of an IC layer, as lithium tungstate isknown to exhibit these properties. But there is also some IC layerfunction in other parts of interfacial region. The inventors have foundthat such “heterogeneous IC layers” improve switching characteristicsand perhaps thermal cycling stability of electrochromic devices ascompared to conventional devices with abrupt transitions. The CE layerin this example contains primarily nickel tungsten oxide as the activematerial, and has a relatively abrupt transition to the nickel tungstenoxide composition at the edge of the interfacial region. Methods formaking stacks with such interfacial regions are described in more detailbelow.

It should be noted that, for example, that the nickel tungsten oxide CElayer in FIG. 2A is depicted as having about 20% lithium tungstate.Without wishing to be bound by theory, it is believed that the nickeltungsten oxide CE layer exists as nickel oxide cores or particlessurrounded by a shell or matrix of lithium tungstate which impartsmoderately good ionic conductivity to the CE layer, and thereby aids inthe electrochromic transition of the CE layer during operation of theelectrochromic stack. The exact stoichiometry of lithium tungstate inthe CE layer may vary significantly from embodiment to embodiment. Insome embodiments, there may also be some tungsten oxide in the CE layer.Also, because lithium ions travel to and from the EC and CE layers viathe interfacial region serving as the IC layer, there may be significantamounts of lithium tungstate in the EC layer, for example as depicted inFIG. 2A.

FIG. 2B depicts an electrochromic stack where the CE material is asignificant component of the interfacial region that functions as an IClayer, while the EC material is not a significant component. Referringto FIG. 2B, starting at the origin and moving from left to right alongthe x-axis, one can see that in this case, the EC material, which issubstantially all tungsten oxide, serves as the EC layer. There is anabrupt transition into the interfacial region where there is little ifany tungsten oxide, but there is a large amount of lithium tungstate andat least some nickel tungsten oxide (CE material). The composition ofthe interfacial region changes along the x-axis with progressively lessand less lithium tungstate and correspondingly more and more nickeltungsten oxide. The transition from the interfacial region to the CElayer is demarked arbitrarily at a composition of about 80% nickeltungsten oxide and about 20% of lithium tungstate, but this is merely anexample of where the transition occurs in a graded composition. Theinterfacial region may be viewed as ending when no, or little,additional change in composition occurs when progressing further throughthe stack. In addition, the transition effectively ends where thecomposition has sufficient quantity of nickel tungsten oxide such thatthe material no longer serves at least some function that a distinct IClayer would serve. Certainly the composition much closer to the CE layeras demarked, where the composition is 80% nickel tungsten oxide, servesthe function of a CE layer. Likewise, the composition of the interfacialregion much closer to the EC layer, where lithium tungstate is thesubstantial component, serves as an ion conductingelectronically-insulating material.

FIG. 2C depicts an electrochromic stack where both the EC material andthe CE material are significant components of the interfacial regionthat functions as an IC layer. Referring to FIG. 2C, starting at theorigin and moving from left to right along the x-axis, one can see thata portion the EC material, WO₃, which is substantially all tungstenoxide, serves as the EC layer. There is a transition into theinterfacial region where there is gradually less tungsten oxide andcorrespondingly gradually more lithium tungstate. In this example, abouta third of the way through what is (arbitrarily) demarked as theinterfacial region, there is also a growing amount of nickel tungstenoxide counter electrode material. At about midway through what isdemarked as the interfacial region, there is about 10% each of tungstenoxide and nickel tungsten oxide and 80% lithium tungstate. In thisexample there is no abrupt transition between an EC layer and an IClayer or between an IC layer and a CE layer, but rather an interfacialregion which has a continuous graded composition of both the CE and ECmaterials. In fact, there is no abrupt boundary or distinct layerpresent, so this example is not actually a stack of materials, butrather a single graded layer comprising an EC region, and IC region anda CE region. This is an example of an EC element. In this example, thelithium tungstate component peaks at about half way through theinterfacial region, and so this region is likely the strongestelectronically-insulating portion of the interfacial region.

As mentioned above in the Summary section, the EC and CE layers mayinclude material components that impart some electrical resistivity tothe EC and CE layers; the lithium tungstate in described in FIGS. 2A-Cthat spans all three regions, at least in some quantity, is an exampleof such materials that impart electrical resistivity to the EC and CElayers.

FIGS. 2A-C represent only three non-limiting examples of gradedcompositions of interfacial regions that serve as IC layers inelectrochromic devices described herein. One of ordinary skill in theart would appreciate that many variations are possible without escapingthe scope of the description. In each of the examples in FIGS. 2A-Cthere is at least one layer where there are only two material componentsand one of the components not present or present only at a level that isde minimus. The invention is not limited in this way. Thus, oneembodiment is an electrochromic device including a electrochromic layer,an interfacial region serving as an IC layer, and a counter electrodelayer, where at least one material component of each of theaforementioned two layers and one region of the device is present ineach of the electrochromic layer, the interfacial region and the counterelectrode layer in a concentration of at least about 25% by weight, inanother embodiment at least about 15% by weight, in another embodimentat least about 10% by weight, in another embodiment at least about 5% byweight, in yet another embodiment at least about 2% by weight. Inanother embodiment, the material component is present at any of theseconcentration ranges in only two of the three layers and region. In thedepicted embodiments, the interface between at least two of the threecomponent layers/regions is not abrupt but exhibits substantialvariation in composition over a region of, for example, at least about20 nm and/or at least about 2% of the total thickness of the EC element.

The amount of electrochromic and/or counter electrode material in theinterfacial region can be significant, in one embodiment as much as 50%by weight of the interfacial region. However, in many embodiments, theion-conducting electronically-insulating material is typically themajority component, while the remainder of the interfacial region iselectrochromic and/or counter electrode material. In one embodiment, theinterfacial region includes between about 60% by weight and about 95% byweight of the ion-conducting electronically-insulating material whilethe remainder of the interfacial region is electrochromic and/or counterelectrode material. In one embodiment, the interfacial region includesbetween about 70% by weight and about 95% by weight of theion-conducting electronically-insulating material while the remainder ofthe interfacial region is electrochromic and/or counter electrodematerial. In one embodiment, the interfacial region includes betweenabout 80% by weight and about 95% by weight of the ion-conductingelectronically-insulating material while the remainder of theinterfacial region is electrochromic and/or counter electrode material.

In some embodiments, interfacial regions in devices described herein maybe relatively distinct, that is, when analyzed, for example bymicroscopy, there are relatively distinguishable boundaries at adjoininglayers, even though the interfacial region contains amounts of theelectrochromic and/or counter electrode material. In such embodimentsthe interfacial region's thickness can be measured. In embodiments wherethe interfacial region is formed from an oxygen-rich(super-stoichiometric) region of an EC and/or CE layer, the ratio of thethickness of the interfacial region as compared to the layer or layersit is formed from is one metric for characterizing the interfacialregion. For example, an electrochromic layer is deposited with anoxygen-rich upper layer. The EC layer may include a single metal oxideor two or more metal oxides mixed homogenously or heterogeneously inlayers or more diffuse regions. The EC layer is 550 nm thick, includingthe oxygen-rich layer (or region). If about 150 nm of the EC layer isconverted to interfacial region, then about 27% of the EC is convertedto interfacial region, that is, 150 nm divided by 550 nm. In anotherexample, the EC layer includes a first metal oxide region (or layer) anda second metal oxide layer (or region) that is oxygen-rich. If all or aportion of the oxygen-rich metal oxide layer is converted to interfacialregion, then the thickness of the interfacial region divided by thetotal thickness of the first and second metal oxide layers (prior toformation of the interfacial region) is a metric for the interfacialregion. In one embodiment, the interfacial region includes between about0.5% and about 50% by thickness of a precursor region (EC and/or CE,including oxygen-rich portion) used to form it, in another embodiment,between about 1% and about 30%, in yet another embodiment, between about2% and about 10%, and in another embodiment between about 3% and about7%.

The inventors have discovered that graded compositions serving as the IClayer have many benefits. While not wishing to be bound by theory, it isbelieved that by having such graded regions, the efficiency of theelectrochromic transitions is improved dramatically. There are otherbenefits as described in more detail below.

While not wishing to be bound to theory, it is believed that one or moreof the following mechanisms may affect the transformation of EC and/orCE material to an IC functioning material in the interfacial region.However, the performance or application of embodiments described hereinis not limited to any of these mechanisms. Each of these mechanisms isconsistent with a process in which IC layer material is never depositedduring fabrication of the stack. As is made clear elsewhere herein,apparatus described herein need not have a separate target comprisingmaterial for an IC layer.

In a first mechanism, the direct lithiation of the electrochromicmaterial or the counter electrode material produces an IC material (forexample, a lithium tungstate) in the interfacial region. As explainedmore fully below various embodiments employ direct lithiation of one ofthe active layers at a point in the fabrication process between theformation of the EC and CE layers. This operation involves exposure ofthe EC or CE layer (whichever is formed first) to lithium. According tothis mechanism, a flux of lithium passing through the EC or CE layerproduces an ionically conductive, electronically resistive material suchas a lithium salt. Heating or other energy can be applied to drive thisflux of lithium. This described mechanism converts the top or exposedportion of the first formed layer (EC or CE layer) prior to formation ofthe second layer (CE or EC layer).

Thus, one embodiment is a method of fabricating an electrochromic deviceincluding: (a) forming either an electrochromic layer including anelectrochromic material or a counter electrode layer including a counterelectrode material; (b) forming an intermediate layer over theelectrochromic layer or the counter electrode layer, where theintermediate layer includes an oxygen rich form of at least one of theelectrochromic material, the counter electrode material and anadditional material, where the additional material includes distinctelectrochromic or counter electrode material, the intermediate layer notsubstantially electronically-insulating; (c) exposing the intermediatelayer to lithium; and (d) heating the stack formed in order to convertat least part of the intermediate layer to a region, coextensive withthe area of the intermediate layer, including anelectronically-insulating ionically-conducting material and the materialof the intermediate layer. The region can include a heterogeneousmixture of the electronically-insulating ionically-conductive materialand the material of the intermediate layer. The additional materialmentioned relates to the fact that sometimes it is desirable to usemixed metal oxides in an electrochromic and/or a counter electrodelayer, rather than a single metal oxide, for example. The nature ofmixed metal oxides in accord with methods and devices described hereinis described in more detail below.

In one embodiment, the electrochromic layer is formed first. In oneembodiment, the electrochromic layer is deposited tungsten oxide. In oneembodiment, depositing tungsten oxide includes sputtering using atungsten target and a first sputter gas including between about 40% andabout 80% O₂ and between about 20% Ar and about 60% Ar, to reach athickness of between about 350 nm and about 450 nm, and heating, atleast intermittently, to between about 150° C. and about 450° C. duringformation of the electrochromic layer. In one embodiment, theelectrochromic layer is substantially polycrystalline WO₃.

In one embodiment, the intermediate layer is a superstoichiometricoxygen form of WO₃. In one embodiment, the superstoichiometric tungstenoxide is deposited via sputtering a tungsten target and a second sputtergas including between about 70% and 100% O₂ and between 0% Ar and about30% Ar, to reach a thickness of between about 10 nm and about 200 nm,without heating.

In one embodiment, (c) includes sputtering lithium onto the intermediatelayer until the blind charge is satisfied and (d) includes heating thestack to between about 100° C. and about 450° C. In another embodiment,(d) includes heating the stack to between about 200° C. and about 350°C., for between about 2 minutes and about 30 minutes. In either of theformer two embodiments, (d) can be performed under an inert atmosphereand/or an oxidizing atmosphere. Examples of inert atmospheres includeargon, nitrogen and the like; oxidizing atmospheres include oxygen andother oxidizing agents.

In some embodiments, rather than two layers of EC or CE material, onenear or at stoichiometric oxygen, a single layer is used, where thelayer has at least a portion that is superstoichiometric in oxygen. Inone embodiment, a graded layer is used where the layer has a graduallyvarying composition with at least a superstoichiometric oxygen upperportion. Thus, another embodiment is a method of fabricating anelectrochromic device including: (a) forming either an electrochromiclayer including an electrochromic material or a counter electrode layerincluding a counter electrode material, where the layer formed includesa superstoichiometric oxygen portion in an upper region of, andcoextensive with, the area of the layer; (b) exposing thesuperstoichiometric oxygen portion to lithium; and (c) heating toconvert at least part of the superstoichiometric oxygen portion to aregion, coextensive with the area of the superstoichiometric oxygenportion and including an electronically-insulating ionically-conductingmaterial and the material of the superstoichiometric oxygen portion. Inone embodiment, the region includes a non-homogeneous mixture of theelectronically-insulating ionically-conducting material and the materialof the superstoichiometric oxygen portion.

In one embodiment, (a) includes forming the electrochromic layer bydepositing tungsten oxide. In one embodiment, depositing tungsten oxideincludes sputtering using a tungsten target and a sputter gas, where thesputter gas includes between about 40% and about 80% O₂ and betweenabout 20% and about 60% Ar at the start of sputtering the electrochromiclayer, and the sputter gas includes between about 70% and 100% O₂ andbetween 0% and about 30% Ar at the end of sputtering the electrochromiclayer, and heating, at least intermittently, to between about 200° C.and about 350° C. at the beginning of formation of the electrochromiclayer but not heated during deposition of at least a final portion ofthe electrochromic layer.

In one embodiment, (b) includes sputtering, or otherwise delivering,lithium onto the intermediate layer until the blind charge is satisfiedand (c) includes heating the stack to between about 100° C. and about450° C. In another embodiment, (c) includes heating the stack to betweenabout 200° C. and about 350° C., for between about 2 minutes and about30 minutes. In either of the former two embodiments, (c) can beperformed under an inert atmosphere and/or an oxidizing atmosphere.Examples of inert atmospheres include argon, nitrogen and the like;oxidizing atmospheres include oxygen and other oxidizing agents.

In either of the two aforementioned methods, that is, using anelectrochromic material having either an intermediatesuperstoichiometric oxygen layer or a single layer with asuperstoichiometric oxygen upper region, further processing includeforming the counter electrode layer on the region. In one embodiment,the counter electrode layer includes NiWO, between about 150 nm andabout 300 nm thick. In one embodiment, the NiWO is substantiallyamorphous. Further processing can include sputtering, or otherwisedelivering, lithium onto the counter electrode layer until the counterelectrode layer is substantially bleached and sputtering an additionalamount of lithium onto the counter electrode layer, between about 5% andabout 15% excess based on the quantity required to bleach the counterelectrode layer. A transparent conducting oxide layer, such as indiumtin oxide, can be deposited on top of the counter electrode layer.

In one embodiment, stacks formed in this way are heated, before or afterdepositing the transparent conducting oxide, at between about 150° C.and about 450° C., for between about 10 minutes and about 30 minutesunder Ar, and then for between about 1 minute and about 15 minutes underO₂. After this processing, the stack is processed further by heating thestack in air at between about 250° C. and about 350° C., for betweenabout 20 minutes and about 40 minutes. Flowing a current between theelectrochromic layer and the counter electrode layer, as part of aninitial activation cycle of the electrochromic device, can also beperformed.

Referring again to the interfacial region formation mechanisms, in asecond mechanism, lithium diffusing from one of the EC or CE to theother layer, after both layers have formed and/or during formation of asecond layer upon a lithiated first layer, causes conversion of part ofone of the EC and/or CE at their interface to the interfacial regionhaving the IC functioning material. The lithium diffusion may take placeafter all the second layer has formed or after only some fraction of thesecond layer has formed. Further, the diffusion of lithium andconsequent conversion to IC functional material take place in either thefirst or second deposited layers and in either the EC or CE layer. Inone example, the EC layer is formed first and then lithiated. As the CElayer is subsequently deposited on top of the EC layer, some lithiumdiffuses from the underlying EC layer toward and/or into the CE layercausing a transformation to an interfacial region which contains an ICfunctioning material. In another example, the EC layer formed first(optionally with an oxygen rich upper region), then the CE layer isformed and lithiated. Subsequently some lithium from the CE layerdiffuses into the EC layer where it forms the interfacial region havingthe IC functioning material. In yet another example, the EC layer isdeposited first and then lithiated to produce some IC functioningmaterial according to first the mechanism described above. Then, whenthe CE layer is formed, some lithium diffuses from the underlying EClayer toward the CE layer to produce some IC material in an interfacialregion of the CE layer. In this manner, the IC functioning materialnominally resides in both the CE and EC layers proximate theirinterface.

Thus, another embodiment is a method of fabricating an electrochromicdevice including: (a) forming either an electrochromic layer includingan electrochromic material or a counter electrode layer including acounter electrode material; (b) forming an intermediate layer over theelectrochromic layer or the counter electrode layer, where theintermediate layer includes an oxygen rich form of at least one of theelectrochromic material, the counter electrode material and anadditional material, where the additional material includes distinctelectrochromic or counter electrode material, the intermediate layer notsubstantially electronically-insulating; (c) exposing the intermediatelayer to lithium; and (d) depositing the other of the electrochromiclayer and the counter electrode layer on the intermediate layer therebyconverting at least part of the intermediate layer to a region,coextensive with the area of the intermediate layer and including anelectronically-insulating ionically-conducting material and theintermediate layer material. In one embodiment, the region includes anon-homogeneous mixture of the electronically-insulatingionically-conducting material and the intermediate layer material.

In one embodiment, the electrochromic layer is formed first and includesdepositing tungsten oxide. In one embodiment, depositing tungsten oxideincludes sputtering using a tungsten target and a first sputter gasincluding between about 40% and about 80% O₂ and between about 20% Arand about 60% Ar, to reach a thickness of between about 350 nm and about450 nm, and heating, at least intermittently, to between about 150° C.and about 450° C. during formation of the electrochromic layer. In oneembodiment, the electrochromic layer is substantially polycrystallineWO₃. In this embodiment, the intermediate layer is a superstoichiometricoxygen form of WO₃, for example, in one embodiment, (b) includessputtering WO₃ using a tungsten target and a second sputter gasincluding between about 70% and 100% O₂ and between 0% Ar and about 30%Ar, to reach a thickness of between about 10 nm and about 200 nm,without heating.

In some embodiments, rather than two layers of EC or CE material, onenear or at stoichiometric oxygen, a single layer is used, where thelayer has at least a portion that is superstoichiometric in oxygen. Inone embodiment, a graded layer is used where the layer has at least asuperstoichiometric oxygen upper portion. Thus, another embodiment is amethod of fabricating an electrochromic device including: (a) formingeither an electrochromic layer including an electrochromic material or acounter electrode layer including a counter electrode material, wherethe layer formed includes a superstoichiometric oxygen portion in anupper region of, and coextensive with, the area of the layer; (b)exposing the superstoichiometric oxygen portion to lithium; and (c)depositing the other of the electrochromic layer and the counterelectrode layer on the superstoichiometric oxygen portion therebyconverting at least part of the superstoichiometric oxygen portion to aregion, coextensive with the area of the superstoichiometric oxygenportion and including an electronically-insulating ionically-conductingmaterial and the material of the superstoichiometric oxygen portion. Inone embodiment, the region includes a non-homogeneous mixture of theelectronically-insulating ionically-conducting material and the materialof the superstoichiometric oxygen portion.

In one embodiment, the electrochromic layer is formed first. In one suchembodiment, the electrochromic layer includes depositing tungsten oxide.In one embodiment, depositing tungsten oxide includes sputtering using atungsten target and a sputter gas, where the sputter gas includesbetween about 40% and about 80% O₂ and between about 20% and about 60%Ar at the start of sputtering the electrochromic layer, and the sputtergas includes between about 70% and 100% O₂ and between 0% and about 30%Ar at the end of sputtering the electrochromic layer, and heating, atleast intermittently, to between about 200° C. and about 350° C. at thebeginning of formation of the electrochromic layer but not heated duringdeposition of at least a final portion of the electrochromic layer. ThisEC layer may also be substantially polycrystalline.

In either of the two aforementioned methods, that is, using anelectrochromic material having either an intermediatesuperstoichiometric oxygen layer or a single layer with asuperstoichiometric oxygen upper region, exposing either theintermediate layer or the superstoichiometric oxygen portion to lithiumcan include sputtering, or otherwise delivering, lithium onto theaforementioned layer or portion. Depositing the other of theelectrochromic layer and the counter electrode layer includes formingthe counter electrode layer on the intermediate layer or thesuperstoichiometric oxygen portion. In one embodiment, the counterelectrode layer includes NiWO, between about 150 nm and about 300 nmthick. In one embodiment, the NiWO is substantially amorphous. Furtherprocessing can include sputtering, or otherwise delivering, lithium ontothe counter electrode layer until the counter electrode layer issubstantially bleached and sputtering an additional amount of lithiumonto the counter electrode layer, between about 5% and about 15% excessbased on the quantity required to bleach the counter electrode layer. Atransparent conducting oxide layer, such as indium tin oxide, can bedeposited on top of the counter electrode layer.

In one embodiment, stacks formed in this way are heated, before or afterdepositing the transparent conducting oxide, at between about 150° C.and about 450° C., for between about 10 minutes and about 30 minutesunder Ar, and then for between about 1 minute and about 15 minutes underO₂. After this processing, the stack is processed further by heating thestack in air at between about 250° C. and about 350° C., for betweenabout 20 minutes and about 40 minutes. Flowing a current between theelectrochromic layer and the counter electrode layer as part of aninitial activation cycle of the electrochromic device can also beperformed.

In a third mechanism, the EC and CE layers are formed to completion (orat least to the point where the second formed layer is partiallycomplete). Then, the device structure is heated and the heating convertsat least some of the material in the interfacial region to an ICfunctioning material (for example, a lithium salt). Heating, for exampleas part of a multistep thermochemical conditioning (MTCC) as describedfurther herein, may be performed during deposition or after depositionis completed. In one embodiment, the heating is performed after atransparent conductive oxide is formed on the stack. In anotherembodiment, heating is applied after the second layer is partially orwholly complete, but before a transparent conductive oxide is appliedthereto. In some cases, the heating is directly and primarilyresponsible for the transformation. In other cases, the heatingprimarily facilitates the diffusion or flux of lithium ions that createsthe IC-functioning material region as described in the second mechanism.

Finally, in a fourth mechanism, current flowing between the EC and CElayers drives the transformation of at least one of the electrochromicmaterial and the counter electrode material to the IC-functioningmaterial in the interfacial region. This may occur because, for example,an ion flux associated with the flowing current is so large it drives achemical transformation of EC and/or CE material to IC material in theinterfacial region. For example, as explained below, a large lithiumflux through tungsten oxide in an EC layer may produce lithiumtungstate, which serves as an IC material. The lithium flux may beintroduced during, for example, an initial activation cycle of a newlyformed device. In one embodiment, the current flow in the initialactivation cycle is used, in lieu of heating, to drive the chemicaltransformation. However, this need not be the case, as otheropportunities for driving high ionic fluxes may be more appropriate foreffecting the conversion. More generally it is the application of anenergy form, for example heat and/or electric current that drives theconversion of the materials to the ionically conductive electronicallyinsulating interfacial region. Other energy forms such as vibrationalenergy, radiant energy, acoustic energy, mechanical energy and the likecan be used. Methods described herein can be performed by one ofordinary skill in the art without resort to any one or more of the abovemechanisms.

As described in relation to FIG. 2C, an EC element has no abrupttransition between an EC layer and an IC layer or between an IC layerand a CE layer, but rather is a single layer graded composition havingan EC region, which transitions to an IC region (the interfacialregion), which transitions to a CE region. Since an EC element is asingle layer of graded composition, EC elements can be described in anumber of ways including those below. The following description is meantto illustrative of certain embodiments of EC elements.

One embodiment is an EC element which is a single layer gradedcomposition including an EC region, an IC region and a CE region,respectively. In one embodiment, the EC element is all solid-state andinorganic. A single EC element can be described in a number of ways inorder to understand the graded composition of which it is comprised. Invarious embodiments, the single layer graded composition EC element hasno abrupt boundaries between EC/IC or between IC/CE. Rather both ofthese interfaces are characterized by graded compositions as discussedherein. In some cases, the single layer graded composition EC elementhas a continuously variable composition across all regions of theelement. In other cases, the element has at least one region, or atleast two regions, of constant composition. FIGS. 2D, 2E and 2F areexamples of how one can metric the composition of one type of ECelement. In these particular examples, the EC element's EC regionincludes a first transition metal; the IC region includes an alkalimetal, and the CE region comprises a mixed transition metal oxide. Inthis particular example, the mixed transition metal oxide includes thefirst transition metal and an additional transition metal, although inother examples, the mixed transition metal oxide does not include thefirst transition metal. In some devices, FIGS. 2D-F are describing thesame EC element, but in different ways. Each of these ways exemplify howone might describe any number of EC elements in accord with embodimentsdescribed herein. In this example, some of the components depicted inthe graphs are present throughout the graded composition, some are not.For example, one transition metal is continuously present in significantconcentration across the entire device, from the EC region, through theCE region. The invention is not limited in this way. In some embodimentssome or all the components are present at least in some de minimusamount (or even a significant amount) throughout the EC element. Incertain examples within the realm of FIGS. 2D-F, each component has atleast some presence in each region of the EC element.

Referring to FIG. 2D, the EC element is described in terms of the molefraction of elemental components from which it is composed as a functionof the region, EC, IC or CE in which the components occur. Starting fromthe origin and moving from left to right across the graph, in the ECregion, there is a higher mole fraction of oxygen (O) than the firsttransition metal (TM₁). For example, this could represent tungsten oxidein approximately a 3:1 ratio of oxygen to tungsten. Moving further tothe right, the mole fraction of oxygen and the first transition metaldecline starting somewhere in the EC region and through the IC regionand into the CE region. At some point in the CE region, the molefraction of oxygen and the first transition metal level off. Forexample, this could represent nickel tungsten oxide of stablecomposition in the CE region. In this example, a second transition metal(TM₂) is present throughout the EC element, in this particular examplehaving a higher mole fraction in the CE region than the other regions ofthe EC element. Also, an alkali metal (M_(alk)) is present in the ECelement. For the purposes of this description, “alkali metal” is meantto encompass both neutral elemental alkali metal and cations thereof,e.g. bound in a material matrix or mobilely associated with the matrixand thus able to intercalate/transport during device operation. In thisexample the alkali metal has the highest mole fraction in the IC region.This might correspond to lithium of lithium tungstate existing in thisregion in one example. It is important to note that the mole fraction ofcomponents depicted in FIG. 2D are those components fixed in the ECelement, e.g., the alkali metal component does not include mobilelithium ions that might be used to drive the EC element to color orbleach (as such ions are mobile and their position in the EC elementwill change depending upon an applied charge, for example). This exampleis illustrative of how one might describe the composition of an ECelement.

One embodiment is an EC element including: a) a first transition metalhaving a higher mole fraction of the composition in the EC region than asecond transition metal, if present, in the EC region, b) an alkalimetal having a maximum mole fraction of the composition in the IC regionas compared to the EC region and the CE region; and c) the secondtransition metal having its maximum mole fraction, of the composition ofany region of the EC element, in the CE region.

Referring to FIG. 2E, if one were to consider the composition of thesame EC element as described in relation to FIG. 2D, but withoutconsidering oxygen content, that is another way to describe embodimentsdescribed herein. For example, in this graph the y-axis is not molefraction, but rather metal concentration; that is, the concentration ofeach metal, TM₁, M_(alk) and TM₂, in each region of the gradedcomposition. In this example, each of the first transition metal and thealkali metal are described in terms of their concentration relative tothe other two metals. The second transition metal is described in termsof its absolute concentration. Referring to FIG. 2E, in the EC region,the first transition metal has its maximum concentration, relative tothe other metals. The alkali metal has its maximum concentration in theIC region, relative to the other metals. The second transition metal hasits maximum (absolute) concentration in the CE region. In this example,TM₁ and TM₂ have substantially the same concentration in the CE region,e.g., this might represent NiWO.

One embodiment is an EC element, including: a) a first transition metalhaving a maximum concentration, relative to other metals in the ECelement, in the EC region, b) an alkali metal having a maximumconcentration, relative to other metals in the EC element, in the ICregion, and c) a second transition metal having its absolute maximumconcentration in the CE region of the EC element.

FIG. 2F describes the composition of the same EC element as described inrelation to FIGS. 2D and 2E, but looking at the actual composition, e.g.compounds, that make up each region. For example, in this graph they-axis is % composition of each compound, oxide of the first transitionmetal (TM₁-oxide), an oxide mixture which includes the alkali metal,along with the first and second transition metals (M_(alk)-TM₁-TM₂ oxidemixture) and a mixed transition metal oxide (TM₁-TM₂ oxide), in eachregion of the graded composition. As mentioned the mixed transitionmetal oxide need not include the first transition metal (e.g. it caninclude a second and third transition metal), but it does in thisexample. The graph in FIG. 2F represents devices including thoserepresented by the specific example described in relation to FIG. 2C. Inthis example, the TM₁-oxide is most abundant in the EC region, and it isthe primary constituent of the EC region. The M_(alk)-TM₁-TM₂ oxidemixture is the primary constituent of the IC region and the TM₁-TM₂oxide is the primary constituent of the CE region. Note that theM_(alk)-TM₁-TM₂ oxide mixture may include more than one compound in amatrix of materials, e.g. this could represent a graded mixture oflithium tungstate, tungsten oxide and nickel tungsten oxide. Themorphology of the EC element may vary across the layer, i.e. the gradedregion may have amorphous portions, crystalline portions and/or mixedamorphous crystalline portions in any one or more of the regions. Insome embodiments, the CE region is substantially amorphous.

One embodiment is an EC element, including: a) a first transition metaloxide which is the primary constituent of the EC region, b) a mixedtransition metal oxide which is the primary constituent of the CEregion, and c) a mixture including the first transition metal and themixed transition metal oxide, the mixture being the primary constituentof the IC region. One embodiment is an EC element, including: a) a firsttransition metal oxide which is the primary constituent of the ECregion, b) a mixed transition metal oxide which is the primaryconstituent of the CE region, and c) a mixture including an alkali metalcompound, the first transition metal and the mixed transition metaloxide, the mixture being the primary constituent of the IC region. Inone embodiment, the mixed transition metal oxide includes the firsttransition metal and a second transition metal selected from the groupconsisting of nickel, tantalum, titanium, vanadium, chromium, cerium,cobalt, copper, iridium, iron, manganese, molybdenum, niobium,palladium, praseodymium, rhodium and ruthenium. In one embodiment, themixed transition metal oxide does not include the first transitionmetal. In one embodiment, the alkali metal is lithium cation, eitherassociated with a compound or associated with the material matrix as atransportable ion during operation of the EC element.

One embodiment is an EC element as described herein in which the firsttransition metal is tungsten and the alkali metal is lithium. In oneembodiment, the EC region is cathodically coloring and the CE region isanodically coloring. In one embodiment, the second transition metal isnickel. In certain embodiments, the EC element includes oxygen in eachof the EC, IC and CE regions. In one embodiment, EC elements describedherein are configured to operate by transport of lithium ions from theCE region, through the IC region and into the EC region, or, from the ECregion, through the IC region and into the CE region, when a potentialis applied across the EC element. In one embodiment, the firsttransition metal oxide is tungsten oxide and the mixed transition metaloxide is nickel tungsten oxide.

One embodiment is an EC device including: a) a first transparentelectrode, b) a second transparent electrode, and c) the EC element asdescribed herein sandwiched therebetween. In one embodiment, the firstand second transparent electrodes include tin oxide based materials. TheEC device may be fabricated on a substrate as described herein; in oneembodiment, the substrate is glass. In one embodiment, the glassincludes a sodium diffusion barrier.

One embodiment is an EC element which is a single layer gradedcomposition including: a) an EC region including primarily tungstenoxide, b) a CE region including primarily nickel tungsten oxide; and,therebetween, c) an IC region including a mixture of lithium tungstate,tungsten oxide and nickel tungsten oxide. One embodiment is an EC deviceincluding the aforementioned EC element. In one embodiment, the ECdevice comprises the EC element sandwiched between two transparentconductive electrodes.

One embodiment is an EC element which is a single layer gradedcomposition including: a) an EC region including a tungsten oxide richmatrix which transitions to a matrix with increasingly more lithiumtungstate, the EC region transitioning to; b) an IC region including amixture of lithium tungstate, tungsten oxide and nickel tungsten oxide,the IC region transitioning, moving away from the EC region, i. frommore to less tungsten oxide; ii. from less to more nickel tungstenoxide; and, iii. having a lithium tungstate rich matrix near a centralportion of the IC region; and c) a CE region which transitions, movingaway from the IC region, from more to less lithium tungstate to a nickeltungsten oxide rich matrix. One embodiment is an EC device including theaforementioned EC element. In one embodiment, the EC device comprisesthe EC element sandwiched between two transparent conductive electrodes.

One embodiment is an EC element as described herein, further including,abutting one of the EC or the CE face of the EC element, a reflectivecoating, a thermochromic coating, a photovoltaic coating or aphotochromic coating. One embodiment is an EC device including theaforementioned EC element. In one embodiment, the EC device comprisesthe EC element sandwiched between two transparent conductive electrodes.In one embodiment, the EC device includes the EC element having only thereflective coating abutting the CE face of the EC element, the ECelement-reflective coating two-layer structure sandwiched between twotransparent conductive electrodes. In one embodiment, the reflectivecoating is an EC coating that becomes reflective anodically andtransparent cathodically. Examples of reflective coatings that may beused for this purpose are described in U.S. Pat. Nos. 7,646,526 and8,031,389, filed Sep. 30, 2008 and Oct. 1, 2008, respectively, which areherein incorporated by reference in their entirety. In one embodiment,the aforementioned EC device is configured to operate by migration oflithium ions from the CE region, through the IC region and into the ECregion, or, from the EC region, through the IC region and into the CEregion, when a potential is applied across the EC element.

Additional EC functionality need not be a discrete layer added onto(abutting) one or both faces of an EC element. One embodiment is an ECelement as described herein, further including, at least one additionalregion selected from the group consisting of a reflective region, athermochromic region and a photochromic region. In one embodiment, theat least one of a reflective region, a thermochromic region or aphotochromic region are on either side of the ECregion-IC-region-CE-region core graded construct. In one embodiment, ananodically-coloring reflective region is included in the EC elementeither between the IC and CE regions or graded into the CE region,opposite the IC region. Exemplary, but non-limiting, anodically coloringreflective materials for this region are described above. In oneembodiment the EC element also includes at least one ion transportregion between the reflective region and neighboring regions, e.g. as abuffer region if the reflective material is somehow incompatible withthe IC region and/or the CE region.

Methods of fabricating EC devices and EC elements are described in moredetail below.

FIG. 3A is a process flow, 300, in accord with methods described herein.Specifically, an EC layer is deposited (on a CL, for example a TCO), see305. Then a CE layer is deposited, see 310. After the EC and CE layersare deposited, then an interfacial region serving as an IC layer isformed therebetween, see 315. One embodiment is an analogous method (notdepicted) where steps 305 and 310 are reversed. The thrust of the methodbeing that the interfacial region, functioning as an IC layer, is formedafter the EC and CE layers, in some embodiments using at least part ofone of the EC and CE layers to make the interfacial region. For thisreason, interfacial regions formed in this way are sometimes referred toas “intrinsic” IC layers. In other embodiments a distinct layer isformed between the EC and CE layers, for example using anoxygen-enriched version of the EC material or the CE material, where thelayer is converted whole or in part to the interfacial region, butagain, after formation of the EC and CE layers. Various methods to formthe interfacial region after the EC-CE stack is formed are describedbelow.

Thus, as mentioned, one embodiment is a method of fabricating anelectrochromic device, the method including: forming an electrochromiclayer including an electrochromic material; forming a counter electrodelayer in contact with the electrochromic layer without first providingan ion conducting electronically-insulating layer between theelectrochromic layer and the counter electrode layer, where the counterelectrode layer includes a counter electrode material; and forming aninterfacial region between the electrochromic layer and the counterelectrode layer, where the interfacial region is substantially ionconducting and substantially electronically-insulating. The interfacialregion can contain component materials of the EC layer, the CE layer orboth. The interfacial region can be formed in a number of ways, asdescribed in more detail below.

FIG. 3B is a process flow, 320, showing a process flow in accord withthe method described in relation to FIG. 3A, in particular, a processflow for depositing an EC layer, then a CE layer and ultimately formingan interfacial region, functioning as an IC layer therebetween. Evenmore particularly, in this embodiment, the EC layer includes WO₃ withvarious amounts of oxygen, in particular compositions andconfigurations; the CE layer includes NiWO, the interfacial regionincludes Li₂WO₄, and TCO materials such as indium tin oxide andfluorinated tin oxide are used. It should be noted that the layers ofthe electrochromic devices are described below in terms of solid statematerials. Solid state materials are desirable because of reliability,consistent characteristics and process parameters and deviceperformance. Exemplary solid state electrochromic devices, methods andapparatus for making them and methods of making electrochromic windowswith such devices are described in U.S. Non-provisional patentapplication Ser. No. 12/645,111, entitled “Fabrication of LowDefectivity Electrochromic Devices,” by Kozlowski et al., and U.S.Non-provisional patent application Ser. No. 12/645,159, entitled“Electrochromic Devices,” by Wang et al., both of which are incorporatedby reference herein for all purposes. In particular embodiments, theelectrochromic devices described herein are all solid state and made inapparatus that allow deposition of one or more layers of the stack in acontrolled ambient environment. That is, in apparatus where the layersare deposited without leaving the apparatus and without, for example,breaking vacuum between deposition steps, thereby reducing contaminantsand ultimately device performance. In a particular embodiment, apparatusdo not require a separate target for depositing an IC layer, as isrequired in conventional apparatus. As one of ordinary skill in the artwould appreciate, the invention is not limited to these materials andmethods, however, in certain embodiments, all of the materials making upelectrochromic stacks and precursor stacks (as described below) areinorganic, solid (i.e., in the solid state), or both inorganic andsolid.

Because organic materials tend to degrade over time, for example whenexposed to ultraviolet light and heat associated with windowapplications, inorganic materials offer the advantage of a reliableelectrochromic stack that can function for extended periods of time.Materials in the solid state also offer the advantage of not havingcontainment and leakage issues, as materials in the liquid state oftendo. It should be understood that any one or more of the layers in thestack may contain some amount of organic material, but in manyimplementations one or more of the layers contains little or no organicmatter. The same can be said for liquids that may be present in one ormore layers in small amounts. It should also be understood that solidstate material may be deposited or otherwise formed by processesemploying liquid components such as certain processes employing sol-gelsor chemical vapor deposition.

Referring again to FIG. 3B, first an EC layer of WO₃ is deposited, see325. FIGS. 4A-4C are schematic cross-sections depicting formation ofelectrochromic devices in accord with specific methods and apparatusdescribed herein, and specifically in accord with process flow 320.Specifically, FIGS. 4A-4C are used to show three non-limiting examplesof how an EC layer including WO₃ can be formed as part of a stack, wherean interfacial region serving as an IC layer is formed after the otherlayers of the stack are deposited. In each of FIGS. 4A-4C, the substrate402, the first TCO layer 404, the CE layer 410 and the second TCO layer412 are essentially the same. Also, in each of the three embodiments, astack is formed without an IC layer, and then the stack is furtherprocessed in order to form an interfacial region that serves as an IClayer within the stack, that is between the EC and the CE layer.

Referring to each of FIGS. 4A-4C, layered structures, 400, 403 and 409,respectively are depicted. Each of these layered structures includes asubstrate, 402, which is, for example, glass. Any material havingsuitable optical, electrical, thermal, and mechanical properties may beused as substrate 402. Such substrates include, for example, glass,plastic, and mirror materials. Suitable plastic substrates include, forexample acrylic, polystyrene, polycarbonate, allyl diglycol carbonate,SAN (styrene acrylonitrile copolymer), poly(4-methyl-1-pentene),polyester, polyamide, etc. and it is preferable that the plastic be ableto withstand high temperature processing conditions. If a plasticsubstrate is used, it is preferably barrier protected and abrasionprotected using a hard coat of, for example, a diamond-like protectioncoating, a silica/silicone anti-abrasion coating, or the like, such asis well known in the plastic glazing art. Suitable glasses includeeither clear or tinted soda lime glass, including soda lime float glass.The glass may be tempered or not. In some embodiments, commerciallyavailable substrates such as glass substrates contain a transparentconductive layer coating. Examples of such glasses include conductivelayer coated glasses sold under the trademark TEC Glass™ by Pilkingtonof Toledo, Ohio, and SUNGATE™ 300 and SUNGATE™ 500 by PPG Industries ofPittsburgh, Pa. TEC Glass™ is a glass coated with a fluorinated tinoxide conductive layer.

In some embodiments, the optical transmittance (i.e., the ratio oftransmitted radiation or spectrum to incident radiation or spectrum) ofsubstrate 402 is about 90 to 95%, for example, about 90-92%. Thesubstrate may be of any thickness, as long as it has suitable mechanicalproperties to support the electrochromic device. While the substrate 402may be of any size, in some embodiments, it is about 0.01 mm to 10 mmthick, preferably about 3 mm to 9 mm thick.

In some embodiments, the substrate is architectural glass. Architecturalglass is glass that is used as a building material. Architectural glassis typically used in commercial buildings, but may also be used inresidential buildings, and typically, though not necessarily, separatesan indoor environment from an outdoor environment. In certainembodiments, architectural glass is at least 20 inches by 20 inches, andcan be much larger, for example, as large as about 72 inches by 120inches. Architectural glass is typically at least about 2 mm thick.Architectural glass that is less than about 3.2 mm thick cannot betempered. In some embodiments with architectural glass as the substrate,the substrate may still be tempered even after the electrochromic stackhas been fabricated on the substrate. In some embodiments witharchitectural glass as the substrate, the substrate is a soda lime glassfrom a tin float line. The percent transmission over the visiblespectrum of an architectural glass substrate (i.e., the integratedtransmission across the visible spectrum) is generally greater than 80%for neutral substrates, but it could be lower for colored substrates.Preferably, the percent transmission of the substrate over the visiblespectrum is at least about 90% (for example, about 90-92%). The visiblespectrum is the spectrum that a typical human eye will respond to,generally about 380 nm (purple) to about 780 nm (red). In some cases,the glass has a surface roughness of between about 10 nm and about 30nm. In one embodiment, substrate 402 is soda glass with a sodiumdiffusion barrier (not shown) to prevent sodium ions from diffusing intothe electrochromic device. For the purposes of this description, such anarrangement is referred to as “substrate 402.”

Referring again to layered structures, 400, 403 and 409, on top ofsubstrate 402 is deposited a first TCO layer, 404, for example made offluorinated tin oxide or other suitable material, that is, among otherthings, conductive and transparent. Transparent conductive oxidesinclude metal oxides and metal oxides doped with one or more metals.Examples of such metal oxides and doped metal oxides include indiumoxide, indium tin oxide, doped indium oxide, tin oxide, doped tin oxide,zinc oxide, aluminum zinc oxide, doped zinc oxide, ruthenium oxide,doped ruthenium oxide and the like. In one embodiment this second TCOlayer is between about 20 nm and about 1200 nm thick, in anotherembodiment, between about 100 nm and about 600 nm thick, in anotherembodiment about 350 nm thick. The TCO layer should have an appropriatesheet resistance (R_(s)) because of the relatively large area spanned bythe layers. In some embodiments, the sheet resistance of the TCO layersis between about 5 and about 30 Ohms per square. In some embodiments,the sheet resistance of TCO layers is about 15 Ohms per square. Ingeneral, it is desirable that the sheet resistance of each of the twoconductive layers be about the same. In one embodiment, the two layers,for example 404 and 412, each have a sheet resistance of about 10-15Ohms per square.

Each of layered structures 400, 403 and 409, include a stack 414 a, 414b and 414 c, respectively, each of which include the first TCO layer 404on top of substrate 402, a CE layer 410, and a second TCO layer 412. Thedifference in each of layered structures 400, 403 and 409 is how the EClayer was formed, which in turn affects the morphology of the resultantinterfacial region in each scenario.

Consistent with process flow 325 of FIG. 3B, each of stacks 414 a, 414 band 414 c include an electrochromic layer deposited on top of the firstTCO layer 404. The electrochromic layer may contain any one or more of anumber of different electrochromic materials, including metal oxides.Such metal oxides include tungsten oxide (WO₃), molybdenum oxide (MoO₃),niobium oxide (Nb₂O₅), titanium oxide (TiO₂), copper oxide (CuO),iridium oxide (Ir₂O₃), chromium oxide (Cr₂O₃), manganese oxide (Mn₂O₃),vanadium oxide (V₂O₅), nickel oxide (Ni₂O₃), cobalt oxide (Co₂O₃) andthe like. In some embodiments, the metal oxide is doped with one or moredopants such as lithium, sodium, potassium, molybdenum, niobium,vanadium, titanium, and/or other suitable metals or compounds containingmetals. Mixed oxides (for example, W-Mo oxide, W—V oxide) are also usedin certain embodiments, that is, the electrochromic layer includes twoor more of the aforementioned metal oxides. An electrochromic layerincluding a metal oxide is capable of receiving ions transferred from acounter electrode layer.

In some embodiments, tungsten oxide or doped tungsten oxide is used forthe electrochromic layer. In one embodiment, the electrochromic layer ismade substantially of WO_(x), where “x” refers to an atomic ratio ofoxygen to tungsten in the electrochromic layer, and x is between about2.7 and 3.5. It has been suggested that only sub-stoichiometric tungstenoxide exhibits electrochromism; i.e., stoichiometric tungsten oxide,WO₃, does not exhibit electrochromism. In a more specific embodiment,WO_(K), where x is less than 3.0 and at least about 2.7 is used for theelectrochromic layer. In another embodiment, the electrochromic layer isWOx, where x is between about 2.7 and about 2.9. Techniques such asRutherford Backscattering Spectroscopy (RBS) can identify the totalnumber of oxygen atoms which include those bonded to tungsten and thosenot bonded to tungsten. In some instances, tungsten oxide layers where xis 3 or greater exhibit electrochromism, presumably due to unboundexcess oxygen along with sub-stoichiometric tungsten oxide. In anotherembodiment, the tungsten oxide layer has stoichiometric or greateroxygen, where x is 3.0 to about 3.5. In some embodiments, at least aportion of the EC layer has an excess of oxygen. This more highlyoxygenated region of the EC layer is used as a precursor to formation ofan ion conducting electron insulating region which serves as an IClayer. In other embodiments a distinct layer of highly oxygenated ECmaterial is formed between the EC layer and the CE layer for ultimateconversion, at least in part, to an ion conductingelectronically-insulating interfacial region.

In certain embodiments, the tungsten oxide is crystalline,nanocrystalline, or amorphous. In some embodiments, the tungsten oxideis substantially nanocrystalline, with grain sizes, on average, fromabout 5 nm to 50 nm (or from about 5 nm to 20 nm), as characterized bytransmission electron microscopy (TEM). The tungsten oxide morphology ormicrostructure may also be characterized as nanocrystalline using x-raydiffraction (XRD) and/or electron diffraction, such as selected areaelectron diffraction (SAED). For example, nanocrystalline electrochromictungsten oxide may be characterized by the following XRD features: acrystal size of about 10 to 100 nm, for example, about 55 nm. Further,nanocrystalline tungsten oxide may exhibit limited long range order, forexample, on the order of several (about 5 to 20) tungsten oxide unitcells.

Thus, for convenience, the remainder of process flow 320, in FIG. 3B,will be further described in relation to a first embodiment, includingformation of EC layer 406, represented in FIG. 4A. Then a second andthird embodiment, represented in FIGS. 4B and 4C, respectively, will bedescribed thereafter with particular emphasis on formation andmorphology and/or microstructure of their respective EC layers.

As mentioned with reference to FIG. 3B, an EC layer is deposited, see325. In a first embodiment (represented in FIG. 4A), a substantiallyhomogeneous EC layer, 406, including WO₃ is formed as part of stack 414a, where the EC layer is in direct contact with a CE layer 410. In oneembodiment, the EC layer includes WO₃ as described above. In oneembodiment, heating is applied during deposition of at least a portionof the WO₃. In one particular embodiment, several passes are made past asputter target, where a portion of the WO₃ is deposited on each pass,and heating is applied, for example to substrate 402, after eachdeposition pass to condition the WO₃ prior to deposition of the nextportion of WO₃ of layer 406. In other embodiments, the WO₃ layer may beheated continually during deposition, and deposition can be done in acontinuous manner, rather than several passes with a sputter target. Inone embodiment, the EC layer is between about 300 nm and about 600 nmthick. As mentioned, the thickness of the EC layer depends on upon thedesired outcome and method of forming the IC layer.

In embodiments described in relation to FIG. 4A, the EC layer is WO₃,between about 500 nm and about 600 nm thick, that is sputtered using atungsten target and a sputter gas including between about 40% and about80% O₂ and between about 20% Ar and about 60% Ar, and where thesubstrate upon which the WO₃ is deposited is heated, at leastintermittently, to between about 150° C. and about 450° C. duringformation of the EC layer. In a particular embodiment, the EC layer isWO₃, about 550 nm thick, sputtered using the tungsten target, where thesputter gas includes about 50% to about 60% O₂ and about 40% to about50% Ar, and the substrate upon which the WO₃ is deposited is heated, atleast intermittently, to between about 250° C. and about 350° C. duringformation of the electrochromic layer. In these embodiments, the WO₃layer is substantially homogenous. In one embodiment, the WO₃ issubstantially polycrystalline. It is believed that heating the WO₃, atleast intermittently, during deposition aids in formation of apolycrystalline form of the WO₃.

As mentioned, a number of materials are suitable for the EC layer.Generally, in electrochromic materials, the colorization (or change inany optical property—for example, absorbance, reflectance, andtransmittance) of the electrochromic material is caused by reversibleion insertion into the material (for example, intercalation) and acorresponding injection of a charge balancing electron. Typically somefraction of the ion responsible for the optical transition isirreversibly bound up in the electrochromic material. As describedherein, some or all of the irreversibly bound ions are used tocompensate “blind charge” in the material. In most electrochromicmaterials, suitable ions include lithium ions (Li⁺) and hydrogen ions(H⁺) (i.e., protons). In some cases, however, other ions will besuitable. These include, for example, deuterium ions (D⁺), sodium ions(Na⁺), potassium ions (K⁺), calcium ions (Ca⁺⁺), barium ions (Ba⁺⁺),strontium ions (Sr⁺⁺), and magnesium ions (Mg⁺⁺). In various embodimentsdescribed herein, lithium ions are used to produce the electrochromicphenomena. Intercalation of lithium ions into tungsten oxide (WO_(3-y)(0<y≦˜0.3)) causes the tungsten oxide to change from transparent(bleached state) to blue (colored state). In a typical process where theEC layer includes or is tungsten oxide, lithium is deposited, forexample via sputtering, on EC layer 406 to satisfy the blind charge (aswill be discussed in more detail below with reference to FIGS. 6 and 7),see 330 of the process flow in FIG. 3B. In one embodiment, thelithiation is performed in an integrated deposition system where vacuumis not broken between deposition steps. It should be noted that in someembodiments, lithium is not added at this stage, but rather can be addedafter deposition of the counter electrode layer or in other embodimentslithium is added after the TCO is deposited.

Referring again to FIG. 4A, next a CE layer, 410, is deposited on EClayer 406. In some embodiments, counter electrode layer 410 is inorganicand/or solid. The counter electrode layer may include one or more of anumber of different materials that are capable of serving as reservoirsof ions when the electrochromic device is in the bleached state. Duringan electrochromic transition initiated by, for example, application ofan appropriate electric potential, the counter electrode layer transferssome or all of the ions it holds to the electrochromic layer, changingthe electrochromic layer to the colored state. Concurrently, in the caseof NiO and/or NiWO, the counter electrode layer colors with the loss ofions.

In some embodiments, suitable materials for the counter electrodesinclude nickel oxide (NiO), nickel tungsten oxide (NiWO), nickelvanadium oxide, nickel chromium oxide, nickel aluminum oxide, nickelmanganese oxide, nickel magnesium oxide, chromium oxide (Cr₂O₃),manganese oxide (MnO₂) and Prussian blue. Optically passive counterelectrodes include cerium titanium oxide (CeO₂—TiO₂), cerium zirconiumoxide (CeO₂—ZrO₂), nickel oxide (NiO), nickel-tungsten oxide (NiWO),vanadium oxide (V₂O₅), and mixtures of oxides (for example, a mixture ofNi₂O₃ and WO₃). Doped formulations of these oxides may also be used,with dopants including, for example, tantalum and tungsten. Becausecounter electrode layer 410 contains the ions used to produce theelectrochromic phenomenon in the electrochromic material when theelectrochromic material is in the bleached state, the counter electrodepreferably has high transmittance and a neutral color when it holdssignificant quantities of these ions. The counter electrode morphologymay be crystalline, nanocrystalline, or amorphous.

In some embodiments, where the counter electrode layer isnickel-tungsten oxide, the counter electrode material is amorphous orsubstantially amorphous. Substantially amorphous nickel-tungsten oxidecounter electrodes have been found to perform better, under someconditions, in comparison to their crystalline counterparts. Theamorphous state of the nickel-tungsten oxide may be obtained though theuse of certain processing conditions, described below. While not wishingto be bound to any theory or mechanism, it is believed that amorphousnickel-tungsten oxide is produced by relatively higher energy atoms inthe sputtering process. Higher energy atoms are obtained, for example,in a sputtering process with higher target powers, lower chamberpressures (i.e., higher vacuum), and smaller source to substratedistances. Under the described process conditions, higher density films,with better stability under UV/heat exposure are produced.

In certain embodiments, the amount of nickel present in thenickel-tungsten oxide can be up to about 90% by weight of the nickeltungsten oxide. In a specific embodiment, the mass ratio of nickel totungsten in the nickel tungsten oxide is between about 4:6 and 6:4, inone example, about 1:1. In one embodiment, the NiWO is between about 15%(atomic) Ni and about 60% Ni, and between about 10% W and about 40% W.In another embodiment, the NiWO is between about 30% (atomic) Ni andabout 45% Ni, and between about 15% W and about 35% W. In anotherembodiment, the NiWO is between about 30% (atomic) Ni and about 45% Ni,and between about 20% W and about 30% W. In one embodiment, the NiWO isabout 42% (atomic) Ni and about 14% W.

In one embodiment, CE layer 410 is NiWO as described above, see 335 ofFIG. 3B. In one embodiment, the CE layer is between about 150 nm andabout 300 nm thick, in another embodiment between about 200 nm and about250 nm thick, in another embodiment about 230 nm thick.

In a typical process, lithium is also applied to the CE layer until theCE layer is bleached. It should be understood that reference to atransition between a colored state and bleached state is non-limitingand suggests only one example, among many, of an electrochromictransition that may be implemented. Unless otherwise specified herein,whenever reference is made to a bleached-colored transition, thecorresponding device or process encompasses other optical statetransitions such non-reflective-reflective, transparent-opaque, etc.Further the term “bleached” refers to an optically neutral state, forexample, uncolored, transparent or translucent. Still further, unlessspecified otherwise herein, the “color” of an electrochromic transitionis not limited to any particular wavelength or range of wavelengths. Asunderstood by those of skill in the art, the choice of appropriateelectrochromic and counter electrode materials governs the relevantoptical transition.

In a particular embodiment, lithium, for example via sputtering, isadded to a NiWO CE layer, see 340 of FIG. 3B. In a particularembodiment, an additional amount of lithium is added after sufficientlithium has been introduced to fully bleach the NiWO, see 345 of FIG. 3B(this process is optional, and in one embodiment excess lithium is notadded at this stage in the process). In one embodiment this additionalamount is between about 5% and about 15% excess based on the quantityrequired to bleach the counter electrode layer. In another embodiment,the excess lithium added to the CE layer is about 10% excess based onthe quantity required to bleach the counter electrode layer. After CElayer 410 is deposited, bleached with lithium and additional lithium isadded, a second TCO layer, 412, is deposited on top of the counterelectrode layer, see 350 of FIG. 3B. In one embodiment, the transparentconducting oxide includes indium tin oxide, in another embodiment theTCO layer is indium tin oxide. In one embodiment this second TCO layeris between about 20 nm and about 1200 nm thick, in another embodiment,between about 100 nm and about 600 nm thick, in another embodiment about350 nm thick.

Referring again to FIG. 4A, once layered structure 400 is complete, itis subjected to thermochemical conditioning which converts at least aportion of stack 414 a to an IC layer (if it was not already converteddue to lithium diffusion or other mechanism). Stack 414 a is aprecursor, not an electrochromic device, because it does not yet have anion conducting/electronically-insulating layer (or region) between EClayer 406 and CE layer 410. In this particular embodiment, in a two stepprocess, a portion of EC layer 406 is converted to IC layer 408 to makea functional electrochromic device 401. Referring to FIG. 3B, layeredstructure 400 is subjected to an MTCC, see 355. In one embodiment, thestack is first subjected to heating, under inert atmosphere (for exampleargon) at between about 150° C. and about 450° C., for between about 10minutes and about 30 minutes, and then for between about 1 minutes andabout 15 minutes under O₂. In another embodiment, the stack is heated atabout 250° C., for about 15 minutes under inert atmosphere, and thenabout 5 minutes under O₂. Next, layered structure 400 is subjected toheating in air. In one embodiment the stack is heated in air at betweenabout 250° C. and about 350° C., for between about 20 minutes and about40 minutes; in another embodiment the stack is heated in air at about300° C. for about 30 minutes. The energy required to implement MTCC neednot be radiant heat energy. For example, in one embodiment ultravioletradiation is used to implement MTCC. Other sources of energy could alsobe used without escaping the scope of the description.

After the multistep thermochemical conditioning, process flow 320 iscomplete and a functional electrochromic device is created. Asmentioned, and while not wishing to be bound by theory, it is believedthat the lithium in stack 414 a along with a portion of EC layer 406and/or CE layer 410 combine to form interfacial region 408 whichfunctions as an IC layer. Interfacial region 408 is believed to beprimarily lithium tungstate, Li₂WO₄, which is known to have good ionconducting and electronically-insulating properties relative totraditional IC layer materials. As discussed above, precisely how thisphenomenon occurs is not yet known. There are chemical reactions thatmust take place during the multistep thermochemical conditioning to formthe ion conducting electronically-insulating region 408 between the ECand CE layers, but also it is thought that an initial flux of lithiumtraveling through the stack, for example provided by the excess lithiumadded to the CE layer as described above, plays a part in formation ofIC layer 408. The thickness of the ion conductingelectronically-insulating region may vary depending on the materialsemployed and process conditions for forming the layer. In someembodiments, interfacial region 408 is about 10 nm to about 150 nmthick, in another embodiment about 20 nm to about 100 nm thick, and inother embodiments between about 30 nm to about 50 nm thick.

As mentioned above, there are a number of suitable materials for makingthe EC layer. As such, using, for example lithium or other suitableions, in the methods described above one can make other interfacialregions that function as IC layers starting from oxygen rich ECmaterials. Suitable EC materials for this purpose include, but are notlimited to SiO₂, Nb₂O₅, Ta₂O₅, TiO₂, ZrO₂ and CeO₂. In particularembodiments where lithium ions are used, ion conducting materials suchas but not limited to, lithium silicate, lithium aluminum silicate,lithium aluminum borate, lithium aluminum fluoride, lithium borate,lithium nitride, lithium zirconium silicate, lithium niobate, lithiumborosilicate, lithium phosphosilicate, and other such lithium-basedceramic materials, silicas, or silicon oxides, including lithiumsilicon-oxide can be made as interfacial regions that function as IClayers.

As mentioned, in one embodiment, the precursor of the ion conductingregion is an oxygen-rich (super-stoichiometric) layer that istransformed into ion-conducting/electron-insulating region vialithiation and MTCC as described herein. While not wishing to be boundto theory, it is believed that upon lithiation, the excess oxygen formslithium oxide, which further forms lithium salts, that is, lithiumelectrolytes, such as lithium tungstate (Li₂WO₄), lithium molybdate(Li₂MoO₄), lithium niobate (LiNbO₃), lithium tantalate (LiTaO₃), lithiumtitanate (Li₂TiO₃), lithium zirconate (Li₂ZrO₃) and the like. In oneembodiment, the interfacial region comprises at least one of tungstenoxide (WO_(3+x), 0≦x≦1.5), molybdenum oxide (MoO_(3+x), 0≦x≦1.5),niobium oxide (Nb₂O_(5+x), 0≦x≦2), titanium oxide (TiO_(2+x), 0≦x≦1.5),tantalum oxide (Ta₂O_(5+x), 0≦x≦2), zirconium oxide (ZrO_(2+x), 0≦x≦1.5)and cerium oxide (CeO_(2+x), 0≦x≦1.5).

Any material, however, may be used for the ion conducting interfacialregion provided it can be fabricated with low defectivity and it allowsfor the passage of ions between the counter electrode layer 410 to theelectrochromic layer 406 while substantially preventing the passage ofelectrons. The material may be characterized as being substantiallyconductive to ions and substantially resistive to electrons. In oneembodiment, the ion conductor material has an ionic conductivity ofbetween about 10⁻¹⁰ Siemens/cm (or ohm⁻¹ cm⁻¹) and about 10⁻³ Siemens/cmand an electronic resistivity of greater than 10⁵ ohms-cm. In anotherembodiment, the ion conductor material has an ionic conductivity ofbetween about 10⁻⁸ Siemens/cm and about 10⁻³ Siemens/cm and anelectronic resistivity of greater than 10¹⁰ ohms-cm. While ionconducting layers should generally resist leakage current (for example,providing a leakage current of not more than about 15 μA/cm², it hasbeen found that some devices fabricated as described herein havesurprising high leakage currents, for example, between about 40 μA/cmand about 150 μA/cm, yet provide good color change across the device andoperate efficiently.

As mentioned above, there are at least two other ways of creating an ionconducting electronically-insulating region between the EC and CElayers, after formation of the stack. These additional embodiments aredescribed below with reference to a particular example where tungstenoxide is used for the EC layer. Also, as mentioned above, theinterfacial region with IC properties may form in situ duringfabrication of the stack when, for example, lithium diffusion or heatconverts some of the EC and/or CE layer to the interfacial region.

In general, there are certain benefits to creating the ion conductingregion later in the process. First, the ion conducting material may beprotected from some of the harsh processing that occurs duringdeposition and lithiation of the EC and CE layers. For example, thedeposition of these layers by a plasma process is often accompanied by alarge voltage drop proximate the stack, frequently in the neighborhoodof 15-20 volts. Such large voltages can damage or cause break down ofthe sensitive ion conducting material. By shifting the IC materialformation to later in the process, the material is not exposed topotentially damaging voltage extremes. Second, by forming the ICmaterial later in the process, one may have better control over someprocess conditions that are not possible prior to completion of both theEC and CE layers. These conditions include lithium diffusion and currentflow between electrodes. Controlling these and other conditions late inthe process provides additional flexibility to tailor the physical andchemical properties of the IC material to particular applications. Thus,not all of the benefits described herein are due to the uniqueinterfacial region acting as an IC layer, that is, there aremanufacturing and other benefits as well.

It has been observed that ion conducting materials formed in accordancewith some of the embodiments described herein have superior performancewhen compared to devices fabricated using conventional techniques forforming an IC layer (for example, PVD from an IC material target). Thedevice switching speed, for example, has been found to be very fast, forexample less than 10 minutes, in one example about eight minutes, toachieve about 80% of end state compared to 20-25 minutes or more fortraditional devices. In some instances, devices described herein haveswitching speeds orders of magnitude better than conventional devices.This is possibly attributable to the greater amounts of readilytransferable lithium disposed in the interfacial region and/or thegraded interfaces, for example between the EC and interfacial regionand/or between the CE and the interfacial region. Such lithium may be inthe EC and/or CE phases intermixed with the IC phase present in theinterfacial region. It is also due possibly to the relatively thin layeror network of IC material present in the interfacial region. In supportof this view, it has been observed that some devices fabricated inaccordance with the teachings herein have high leakage currents, yetsurprisingly exhibit good color change and good efficiency. In somecases, the leakage current density of solidly performing devices hasbeen found to be at least about 100 μA/cm. In some embodiments, ECdevices and EC elements may have leakage currents as low as 10 μA/cm orless.

Referring now to FIG. 4B, in a second embodiment, the initially laiddown EC material of stack 414 b is really two layers: a first WO₃ layer,406, analogous to layer 406 in FIG. 4A, but between about 350 nm andabout 450 nm thick, that is sputtered using a tungsten target and afirst sputter gas including between about 40% and about 80% O₂ andbetween about 20% Ar and about 60% Ar, and a second WO₃ layer, 405,between about 100 nm and about 200 nm thick, that is sputtered using thetungsten target and a second sputter gas including between about 70% and100% O₂ and between 0% Ar and about 30% Ar. In this embodiment, heat isapplied, for example by heating substrate 402, at least intermittently,to between about 150° C. and about 450° C. during deposition of thefirst WO₃ layer, 406, but not, or substantially not, heated duringdeposition of the second WO₃ layer 405. In a more specific embodiment,layer 406 is about 400 nm thick and the first sputter gas includesbetween about 50% and about 60% O₂ and between about 40% and about 50%Ar; the second WO₃ layer 405 is about 150 nm thick and the secondsputter gas is substantially pure O₂. In this embodiment, heat isapplied, at least intermittently, to between about 200° C. and about350° C. during formation of the first WO₃ layer, 406, but not, orsubstantially not, heated during formation of the second WO₃ layer 405.In this way, the first WO₃ layer is substantially polycrystalline, whilethe second WO₃ layer is not necessarily so.

Referring again to FIG. 4B, as described above in relation to FIGS. 3Band 4A, the stack is completed by lithiation of EC layer(s) 406 and 405to approximately or substantially satisfy the blind charge, depositionof CE layer 410, lithiation of the CE layer to bleach state, addition ofadditional lithium, and deposition of the second TCO layer 412 tocomplete layered stack 403. Analogous thermochemical conditioning isperformed on layered stack 403 to provide layered stack 407, afunctional electrochromic device including an ion conductingelectronically-insulating region 408 a. While not wishing to be bound bytheory, in this example, it is believed that the oxygen rich layer 405of WO₃ serves primarily as the source of precursor material to forminterfacial region 408 a. In this example, the entire oxygen rich WO₃layer is depicted as converting to interfacial region 408 a, however ithas been found that this is not always the case. In some embodiments,only a portion of an oxygen rich layer is converted to form aninterfacial region that serves the function of an IC layer.

Referring now to FIG. 4C, in a third embodiment, layered stack 409includes an EC layer, 406 a, which has a graded composition of WO₃ andis formed as part of a stack, 414 c, where the graded compositionincludes varying levels of oxygen. In one non-limiting example, there isa higher concentration of oxygen in EC layer 406 a at the EC-CE layer(410) interface than, for example, at the interface of TCO layer 404with EC layer 406 a.

In one embodiment, EC layer 406 a is a graded composition WO₃ layer,between about 500 nm and about 600 nm thick, that is sputtered using atungsten target and a sputter gas, where the sputter gas includesbetween about 40% and about 80% O₂ and between about 20% Ar and about60% Ar at the start of sputtering the electrochromic layer, and thesputter gas includes between about 70% and 100% O₂ and between 0% Ar andabout 30% Ar at the end of sputtering the electrochromic layer, andwhere heat is applied, for example to substrate 402, at leastintermittently, to between about 150° C. and about 450° C. at thebeginning of formation of EC layer 406 a but not, or substantially not,applied during deposition of at least a final portion of EC layer 406 a.In a more specific embodiment, the graded composition WO₃ layer is about550 nm thick; the sputter gas includes between about 50% and about 60%O₂ and between about 40% and about 50% Ar at the start of sputtering theelectrochromic layer, and the sputter gas is substantially pure O₂ atthe end of sputtering the electrochromic layer; and where heat isapplied, for example to substrate 402, at least intermittently, tobetween about 200° C. and about 350° C. at the beginning of formation ofthe electrochromic layer but not, or substantially not, applied duringdeposition of at least a final portion of the electrochromic layer. Inone embodiment heat is applied at the described temperature ranges atthe onset of deposition and gradually decreased to no applied heat at apoint where about half of the EC layer is deposited, while the sputtergas composition is adjusted from between about 50% and about 60% O₂ andbetween about 40% and about 50% Ar to substantially pure O₂ along asubstantially linear rate during deposition of the EC layer.

More generally, the interfacial region typically, though notnecessarily, has a heterogeneous structure that includes at least twodiscrete components represented by different phases and/or compositions.Further, the interfacial region may include a gradient in these two ormore discrete components such as an ion conducting material and anelectrochromic material (for example, a mixture of lithium tungstate andtungsten oxide). The gradient may provide, for example, a variablecomposition, microstructure, resistivity, dopant concentration (forexample, oxygen concentration), stoichiometry, density, and/or grainsize regime. The gradient may have many different forms of transitionincluding a linear transition, a sigmoidal transition, a Gaussiantransition, etc. In one example, an electrochromic layer includes atungsten oxide region that transitions into a superstoichiometrictungsten oxide region. Part, or all, of the superstoichiometric oxideregion is converted to the interfacial region. In the final structure,the tungsten oxide region is substantially polycrystalline and themicrostructure transitions to substantially amorphous at the interfacialregion. In another example, an electrochromic layer includes a tungstenoxide region that transitions into a niobium (superstoichiometric) oxideregion. Part, or all, of the niobium oxide region is converted to theinterfacial region. In the final structure, the tungsten oxide region issubstantially polycrystalline and the microstructure transitions tosubstantially amorphous at the interfacial region.

Referring again to FIG. 4C, as described above in relation to FIGS. 3Band 4A, the stack is completed by lithiation of EC layer 406 a toapproximately or substantially satisfy the blind charge, deposition ofCE layer 410, lithiation of the CE layer to bleach state, addition ofadditional lithium, and deposition of the second TCO layer 412 tocomplete layered stack 409. Analogous multistep thermochemicalconditioning is performed on layered stack 409 to provide layered stack411, a functional electrochromic device including an ion conductingelectronically-insulating region 408 b and at least a portion oforiginal graded EC layer 406 a which serves as the EC layer in thefunctional electrochromic device 411. While not wishing to be bound bytheory, in this example, it is believed that uppermost oxygen richportion of the graded layer of WO₃ primarily forms graded interfacialregion 408 b. While not wishing to be bound by theory, there is thepossibility that formation of the interfacial region is self-limitingand depends on relative amounts of oxygen, lithium, electrochromicmaterial and/or counter electrode material in the stack.

In various embodiments described herein, the electrochromic stack isdescribed as not, or substantially not, being heated during certainprocessing phases. In one embodiment, the stack is cooled, actively orpassively (for example using a heat sink), after a heating step.Apparatus described herein include active and passive coolingcomponents, for example, active cooling can include platens that arecooled via fluid circulation, cooling via exposure to cooled (e.g. viaexpansion) gases, refrigeration units and the like. Passive coolingcomponents can include heat sinks, such as blocks of metal and the like,or simply removing the substrate from exposure to heat.

Another embodiment is a method of fabricating an electrochromic device,the method including: (a) forming either an electrochromic layerincluding an electrochromic material or a counter electrode layerincluding a counter electrode material; (b) forming an intermediatelayer over the electrochromic layer or the counter electrode layer,where the intermediate layer includes an oxygen rich form of at leastone of the electrochromic material, the counter electrode material andan additional material, where the additional material includes distinctelectrochromic or counter electrode material, where the intermediatelayer is not substantially electronically-insulating; (c) forming theother of the electrochromic layer and the counter electrode layer; and(d) allowing at least a portion of the intermediate layer to becomesubstantially electronically-insulating. In one embodiment, theelectrochromic material is WO₃. In another embodiment, (a) includessputtering WO₃ using a tungsten target and a first sputter gas includingbetween about 40% and about 80% O₂ and between about 20% Ar and about60% Ar, to reach of thickness of between about 350 nm and about 450 nm,and heating, at least intermittently, to between about 150° C. and about450° C. during formation of the electrochromic layer. In anotherembodiment, (b) includes sputtering WO₃ using a tungsten target and asecond sputter gas including between about 70% and 100% O₂ and between0% Ar and about 30% Ar, to reach a thickness of between about 100 nm andabout 200 nm, without heating. In yet another embodiment, the methodfurther includes sputtering lithium onto the intermediate layer untilthe blind charge is approximately or substantially satisfied. In oneembodiment, the counter electrode layer includes NiWO, between about 150nm and about 300 nm thick. In another embodiment, lithium is sputteredonto counter electrode layer until the counter electrode layer isbleached. In another embodiment, an additional amount of lithium,between about 5% and about 15% excess based on the quantity required tobleach the counter electrode layer, is sputtered onto the counterelectrode layer. In another embodiment, a transparent conducting oxidelayer is deposited on top of the counter electrode layer. In oneembodiment the transparent conducting oxide includes indium tin oxide,in another embodiment, the transparent conducting oxide is indium tinoxide. In another embodiment, the stack formed from the aboveembodiments is heated at between about 150° C. and about 450° C., forbetween about 10 minutes and about 30 minutes under Ar, and then forbetween about 1 minutes and about 15 minutes under O₂, and then heatedin air at between about 250° C. and about 350° C., for between about 20minutes and about 40 minutes.

In another embodiment, (a) includes sputtering a first electrochromicmaterial of formula MO_(x), where M is a metal or metalloid element andx indicates stoichiometric oxygen to M ratio, and (b) includessputtering a second electrochromic material of formula NO_(y) as theintermediate layer, where N is the same or a different metal ormetalloid element and y indicates a superstoichiometric amount of oxygento N ratio. In one embodiment, M is tungsten and N is tungsten. Inanother embodiment, M is tungsten and N is selected from the groupconsisting of niobium, silicon, tantalum, titanium, zirconium andcerium.

Another embodiment is an electrochromic device including: (a) anelectrochromic layer including an electrochromic material; (b) a counterelectrode layer including a counter electrode material; and (c) aninterfacial region between the electrochromic layer and the counterelectrode layer, where the interfacial region includes anelectronically-insulating ion conducting material and at least one ofthe electrochromic material, the counter electrode material and anadditional material, where the additional material includes distinctelectrochromic or counter electrode material.

In one embodiment, the electronically-insulating ion conducting materialand at least one of the electrochromic materials, the counter electrodematerial and the additional material are substantially evenlydistributed within the interfacial region. In another embodiment, theelectronically-insulating ion conducting material and at least one ofthe electrochromic material, the counter electrode material and theadditional material include a composition gradient in a directionperpendicular to the layers. In another embodiment, consistent witheither of the two aforementioned embodiments, theelectronically-insulating ion conducting material includes lithiumtungstate, the electrochromic material includes a tungsten oxide and thecounter electrode material includes nickel tungsten oxide. In a specificimplementation of the aforementioned embodiment, there is no additionalmaterial. In one embodiment, the electrochromic layer is between about300 nm and about 500 nm thick, the interfacial region is between about10 nm and about 150 nm thick, and the counter electrode layer is betweenabout 150 nm and about 300 nm thick. In another embodiment, theelectrochromic layer is between about 400 nm and about 500 nm thick; theinterfacial region is between about 20 nm and about 100 nm thick, andthe counter electrode layer is between about 150 and about 250 nm thick.In yet another embodiment, the electrochromic layer is between about 400nm and about 450 nm thick; the interfacial region is between about 30 nmand about 50 nm thick, and the counter electrode layer is about 200 nmand about 250 nm thick.

Another embodiment is a method of fabricating an electrochromic device,the method including: depositing an electrochromic layer by sputtering atungsten target with a sputter gas comprising between about 40% andabout 80% O₂ and between about 20% Ar and about 60% Ar to produce WO₃ toa thickness of between about 500 nm and about 600 nm, where thesubstrate upon which the WO₃ is deposited is heated, at leastintermittently, to between about 150° C. and about 450° C. duringformation of the electrochromic layer; sputtering lithium onto theelectrochromic layer until the blind charge is satisfied; depositing acounter electrode layer on the electrochromic layer without firstproviding an ion conducting electronically-insulating layer between theelectrochromic layer and the counter electrode layer, where the counterelectrode layer includes NiWO; sputtering lithium onto the counterelectrode layer until the counter electrode layer is substantiallybleached; and forming an interfacial region between the electrochromiclayer and the counter electrode layer, where the interfacial region issubstantially ion conducting and substantiallyelectronically-insulating. In one embodiment, forming the interfacialregion includes MTCC of the stack, alone or along with substrate,conductive and/or encapsulation layers.

The description in relation to FIGS. 4A-C was in relation to EC devices,that is, in terms of at least two distinct layers existing in the devicearchitecture. As described, certain embodiments include EC elementswhere there is only a single layer of graded material that serves thefunction of an EC device or stack. FIG. 4D depicts one such EC element,421, which is part of an EC device 413. The EC element 421 is a singlelayer graded composition, having a cathodically coloring EC region, 417,which transitions to an IC region, 418 (an interfacial region asdescribed herein), which transitions to an anodically coloring CEregion, 419. The EC element 421 is sandwiched between two transparentconducting oxide (TCO) electrodes, 404 and 412. Device fabrication inthis example includes depositing TCO 404 on substrate 402, thedepositing EC element 421 on TCO 404, followed by deposition of TCO 412on EC element 421. Thus, EC device 413 has only three layers, EC element421 sandwiched between TCO's 404 and 412. Fabrication of EC elements isdescribed in more detail below.

In a broad sense, an EC element is a single layer EC device stack havingsuccessive functional regions as opposed to distinct layers where thereis an abrupt material change between layers and de minimus materialmixing between successive layers. Rather, an EC element has successivefunctional regions where there is more than de minimus material mixingbetween each successive functional region. In certain embodiments, e.g.as described in relation to possible mechanisms for formation of aninterfacial region serving as an IC layer, fabrication of an EC elementcan include judicious choice of materials, where the materials are laiddown in a conventional sense, in layers, but where the material choiceand/or subsequent processing promotes material mixing and/or chemicaland/or morphological changes that transform the interfaces betweensuccessive layers into graded regions, and thus, what starts as a stackof layers is transformed into an EC element.

In other embodiments, fabrication of an EC element includes depositing,e.g. sputtering, materials in the vapor phase to deposit successivefunctional regions in an EC element, where there is more than de minimusmaterial mixing between successive functional regions during thedeposition process, that is, in the vapor phase, e.g. materials forsuccessive functional regions are co-sputtered at least for a periodbetween sputtering of the first material and sputtering of the secondmaterial. In the example of all sputter deposited materials, this resultmay be accomplished by, e.g., using sputter targets having theappropriate composition and configuration such that material mixing islimited to some fraction of each of the successive functional regions.That is, the functional regions are composed primarily of some material(which itself may be a graded composition) and this material isdeposited to form the bulk of the function region. For example, materialmixing occurs during transition from sputtering a first material, fromwhich a first functional region is comprised, to sputtering a secondmaterial, from which the next successive functional region is comprised.There is some mixing (co-sputtering) during this transition between thetwo materials, which ceases at some point, and then the second materialis sputtered for a period, followed by a transition where the secondmaterial is sputtered along with a third material. The transition fromthe second functional region to the third function region includesco-sputter of the second and third materials. The third material issputtered alone for a period, followed by the next transition if thereis a fourth material, and so on. In certain embodiments, the materialmixing occurs in the vapor phase, prior to the materials being deposited(although there may be further mixing and/or morphological changes afterdeposition). Particular embodiments for achieving sputtering profilesfor creating EC elements are described below.

One embodiment is a method of fabricating a single layer gradedcomposition EC element on a substrate in a sputter system, including: a)sputter coating an EC material including a first transition metal and afirst oxygen concentration onto the substrate; b) increasing from thefirst oxygen concentration to a second oxygen concentration, higher thanthe first, during a); c) introducing lithium into the sputter system;and d) sputter coating a CE material including a second transition metaland oxygen; wherein the fabrication is a substantially continuousprocess and the concentration of the first transition metal is decreasedfrom a) to d), and the concentration of the second transition metal isincreased from a) to d). In one embodiment, the first transition metalis tungsten. In one embodiment, the second transition metal is nickel.In one embodiment, introducing lithium into the sputter system includessputtering target comprising a lithium compound. In one embodiment, thelithium compound is lithium tungstate.

Methods of fabricating EC elements described herein can be performed,for example, using a sputter system having capability of introducingtargets and/or target materials during plasma sputter. Another way toaccomplish these methods is to arrange a series of targets, insubstantially contiguous fashion, where the targets' compositionreflects the composition of the desired graded EC element, and pass thesubstrate pass the targets during sputter (and/or pass the targets pastthe substrate during sputter). Yet another way of performing thesemethods is to sputter from a single a target, the composition of whichreflects the composition of the desired graded EC element. Theseembodiments are described in more detail below.

One embodiment is a method of fabricating a single layer gradedcomposition EC element on a substrate in a sputter system, includingsputter coating materials from a plurality of closely associated sputtertargets such that there is mixing of materials sputtered from eachtarget in the region where two targets are proximate each other; wherethe single layer EC element is fabricated upon a single pass of thesubstrate and the plurality of closely associated sputter targets pasteach other.

FIG. 4E depicts a target assembly, 421, which may be used to fabricatean EC element as described herein. Target assembly 421 includes abacking plate, 420, on which are affixed three target sections, an ECtarget section, 425, an IC target section, 430, and a CE target section,435. Each of the target sections comprises a material reflective of themajority constituent of the deposited region to which they correspond. Asubstrate, 431, is translated past target assembly 421 as depicted bythe heavy dashed arrow. One of ordinary skill in the art wouldappreciate that three separate targets, each with their own power supplyand backing plate, for example, would also work, so long as the targetswere proximate during sputter deposition such that there was some mixingof materials from the sputter plasmas in the areas near contiguoustarget edges. For the purposes of this description the term “closelyassociated sputter targets” is meant to include these possibilities.Also, although FIG. 4E depicts linear edges of the target sectionsproximate and parallel to each other, this need not be so. For example,the adjoining (or proximate) edges of targets could be curved, zig zagor other complementary (or not) shapes to enhance plasma and thusmaterial mixing in the deposited layer. Also, although in this examplethere are three target sections, this need not be so. For example theremay be many target sections, reflective of the graded composition alongthe sputter deposition path, for example, of varying widths, shapes andcompositions depending upon the desired outcome. The width of thetarget, speed of translation of the substrate and/or target past eachother, sputter power, etc. will determine the characteristics of thedeposited single film graded composition. The plurality of closelyassociated sputter targets need not be planar targets, but may be rotarytargets or combinations of planar, rotary and other target types and/orshapes appropriate to effect the desired outcome in the gradedcomposition.

Referring again to FIG. 4E, as indicated by the heavy dashed arrow,substrate 431 and target assembly are translated relative to each other,for example the substrate is passed along and in front of the targetassembly, during sputter deposition. As the substrate moves along thetarget, a single layer graded composition that functions as an EC deviceis deposited on the substrate. In one embodiment, a plurality of closelyassociated sputter targets includes a target including an EC material, atarget including an IC material and a target including a CE material. Inone embodiment, the EC material includes tungsten oxide. In oneembodiment, the IC material includes lithium tungstate. In oneembodiment, the CE material includes nickel tungsten oxide.

As described above, another embodiment is a method of fabricating asingle layer graded composition EC element on a substrate in a sputtersystem, including sputter coating materials from a single sputter targetincluding a composition substantially reflective of the single layer ECelement; wherein the single layer EC element is fabricated upon a singlepass of the substrate and the single sputter target past each other.This is illustrated in FIG. 4F. Target assembly 422 includes a backingplate 420, to which is affixed a sputter target, 440. Sputter target 440has a composition reflective of the desired EC element to be deposited.During sputtering, a substrate is translated past sputter target 440 ina single pass, during which the EC element is deposited. The singletarget can be manufactured, e.g., by sintering together materials foreach of the respective regions of the EC element. In one embodiment,target sub-sections are sintered together; that is, smaller pre-formedtarget sections are sintered and/or fused together into the singletarget. The individual target sections that are sintered into a singletarget may have straight edges prior to sintering together, e.g. targetsections as depicted in relation to FIG. 4E. In other embodiments, theindividual target sub-sections are interleaved at the abutting edges,e.g. as depicted in FIG. 4F, line 421, prior to sintering. That is, thetarget sub-sections may fit together, e.g. like postage stamps, havinginterleaved edges. In certain embodiments, interleaving provides forbettering mixing of materials at the transition between two materials inthe EC element (thus in one embodiment, the interleaving obviates theneed for sintering sections into a single target). The interleaving canbe of any shape, e.g. curved as line 421 suggests, or zig-zag,rectangular interlocking, and the like. Also, the interleaving can begross, having large interleaving features and/or very fine or smallinterleaving features, e.g. prismatically interleaved surfaces areabutted and the target sub-sections sintered together.

In one embodiment, the single sputter target includes a region of ECmaterial, which is graded into a region of IC material, which is gradedinto a region of CE material. In one embodiment, the region of ECmaterial includes tungsten oxide. In one embodiment, the region of ICmaterial includes lithium tungstate. In one embodiment, the region of CEmaterial includes nickel tungsten oxide.

In the description above, an EC element is often described in terms of asingle layer graded composition having an EC region, an IC region and aCE region. In certain embodiments, this EC element is described as beingsandwiched between two transparent conducting oxide (TCO) electrodes inorder to form an EC device. FIG. 4G illustrates a target arrangement,423, that can be used to fabricate such an EC device. In thisarrangement, target assembly 422, as described in relation to FIG. 4F,is situated between two separate targets, 450 having a backing plate445, and 460 having a backing plate 455. Assuming there is no mixing ofmaterials between targets 450, 440 and 460 during sputtering, an ECelement sandwiched between two TCO layer electrodes will be formed in asingle pass sputter deposition. However, if targets 450 and 460 areproximate target 440 such that there is material mixing by design duringsputtering, then an EC element such as described in relation to FIG. 4His formed.

FIG. 4H is a cross section schematic of an EC element, 442. EC element442 is a single layer graded composition having a first TCO region, 404a, a cathodically coloring EC region, 417 a, an IC region, 418 a, ananodically coloring CE region, 419 a and a second TCO region, 412 a.Once appropriately lithiated (during formation of EC element 442, ornot), as depicted, a potential can be applied across EC element 442 andit will function as a conventional EC device. However, EC element 442 isa single layer graded composition, deposited in a single pass on asubstrate. This is a radical departure from conventional fabricationmethods and EC structure. Using the methods described herein, one cancoat a single layer of material on a substrate, where the materialbehaves as a conventional EC device would. This saves considerableprocessing steps and the result is highly desirable—a single layer filmswitchable coating, e.g. one that includes complementary coloringfunctional regions. One advantage of such a construct is thatdelamination resulting from adhesion issues between material layers isavoided. Of course, as described above, there are various targetarrangements that can accomplish these methods.

As described in relation to FIG. 4G, if the target sections areappropriately spaced one can fabricate an EC element such as thatdescribed in relation to FIG. 4H. Alternatively, a target assembly, 424,as depicted in FIG. 4I could be used. Target assembly 424 includes asingle backing plate, 465, on which are mounted a plurality of targetsections, 470-490, whose composition correspond to the regions of thedesired EC element on the substrate post sputter. In this example, theneighboring target sections are abutting or in close proximity with eachother. The abutting or closely neighboring edges may not be straight asdepicted, but may include interleaving as described in relation to FIG.4F. One embodiment is a method of fabricating an EC element includingfive successive functional regions: a first transparent conductorregion, a cathodically coloring electrochromic region, an ion conductingregion, an anodically coloring electrochromic region and a secondtransparent conductor region; the method comprising substantiallycontinuous sputtering during formation of the five successive functionalregions.

FIG. 4J shows yet another alternative, sputter target assembly 426,which is a plurality of closely associated sputter targets, 491-495,e.g. each with their own backing plate and associated power supply andmagnetic source, whose composition correspond to the regions of thedesired EC element on the substrate post sputter. Targets 491-495 areconfigured so that there is material mixing by design of the plasmas foreach target in the regions between the targets. Conventional thought isto have complete isolation and control of sputter plasma geometry suchthat a substrate can be passed by the sputter target and a film ofhighly uniform composition, reflecting the target and sputter gascomposition is deposited. In embodiments described herein, materialmixing of adjacent plasma and/or material deposited on a substrate is bydesign so that a single layer graded composition results. One ofordinary skill in the art would appreciate that various targetarrangements and materials are possible without deviating from the scopeof the description. For example, rather than five target sections asdepicted in FIG. 4I, the first TCO target section may be obviated if thesubstrate is, e.g., float glass with a TCO, e.g. a fluorinated tin oxidepyrolytic coating, already deposited (the result would be in thisexample, an EC device because there are two layers, the TCO and an ECelement with four regions). In another example, rather than five sputtertargets, as depicted in FIG. 4J, one might choose to use ten targets,e.g., of less width but having overall substantially the same collectivewidth, for more material mixing throughout the deposition and thus inthe deposited single layer graded composition. Lithium sputter targets(not depicted) may also be included at various positions in the targetarrangement. In yet another example, a reflective region, athermochromic region, a photochromic region, and/or a photovoltaicregion may be desired. In this example, targets are configured and/orarranged so that corresponding reflective, thermochromic, photochromicand/or photovoltaic regions are incorporated in the EC element.

FIG. 4K shows yet another alternative, sputter target assembly 427,which is a plurality of closely associated rotary sputter targets, 472,473, 474, 476 and 478, e.g. each with their own associated power supplyand magnetic source, whose composition correspond to the regions of thedesired EC element on substrate 431 post sputter. The rotary targets areconfigured so that there is material mixing by design of the plasmas foreach target in the regions between the targets. In this example, thereare baffles, 471, between each rotary target. Baffles 471 may bemovable, in order to attenuate or augment material mixing in the regionbetween neighboring rotary targets. The baffles may be movedperpendicular to the substrate, toward or away from the substrate and/oralong an axis parallel to the substrate, between two rotary targets,such that the separation between the baffle and any two targets oneither side can be controlled. By being able to move the baffles in thismanner, the material mixing in the region between neighboring targetscan be controlled and designed for the desired result. The baffles maynot have straight edges as depicted, i.e., they may have edges withcurved edges, jagged edges, rectangular cuts, etc. in order to mediatematerial mixing in the region between targets. In addition to, or in thealternative to baffles, sputter targets (planar or rotary) may beconfigured to move toward and away from each other and/or toward andaway from the substrate during sputter deposition. The rotary targets inFIG. 4K are depicted as rotating in the same direction, but this is butone embodiment. In other embodiments, the rotary targets may turn inalternating directions or in any combination, e.g., two clockwise, onecounter clockwise, two clockwise, etc.

FIG. 4L shows yet another alternative, sputter target assembly 428,which is a plurality of closely associated sputter targets, 482, 483,484, 485 and 486, e.g. each with their own associated power supply andmagnetic source, whose composition correspond to the regions of thedesired EC element on a substrate post sputter. This example shows amixture of planar sputter targets and rotary targets. In this example,rotary targets 483 and 485 rotate opposite each other. The neighboringtargets may have baffles as described above or not. The order and numberof rotary and planar targets may vary, depending upon the desiredsputter outcome. For example, there may be two planar targets and threerotary targets or four planar targets and one rotary target. Mixingrotary and planar targets allows for greater flexibility in processdesign and control. Parameters related to sputter deposition of an ECelement are described in more detail below.

Certain embodiments described herein include using a plurality ofseparate sputter targets arranged in close proximity in order to createoverlapping zones of different material plasmas which allows fabricationof an EC element. FIG. 4M depicts various geometries as they relate toprocess parameters in relation to two planar sputter targets in closeproximity and a substrate translating past the targets. The distancebetween the sputter targets, α, is one factor that affects materialmixing in the sputter plasmas. The distance between the sputter targetswill be a factor in the amount of overlap of plasma densities (asdepicted by the curved dotted lines radiating from each target. Also,the shape and density of the plasma from each target will be affected bythe magnetic field shape and strength (the black rectangles representthe magnets of the cathode) as well as the pressure and power densityused to generate the plasma. The distance between the sputter target andthe substrate, β, is another parameter that affects how proximatesputter plasmas will mix. The distance between the target and thesubstrate will determine how dense the plasma impinging on the substratewill be. The distance β can be varied to increase or decrease thedensity of the plasma impinging on the substrate, for example, by movingthe targets toward, or away from, the substrate; moving the substratetoward, or away from the targets, or both.

In certain embodiments, the relationship between distances α and β arechosen to impact the density and shape of the plasmas as well as thedesired deposition profile. In one embodiment, for deposition usingoptimally-mixed plasmas between two targets, the ratio of β to α isbetween about 1 and about 10, in another embodiment between about 1.5and about 5, and in another embodiment between about 2 and about 5. Theplasma densities depicted in FIG. 4M are merely representative. In thisexample, the plasma densities are drawn as symmetrical and equivalent inshape. This is not necessary. For example, as described, the plasmas areof different materials (as reflected by the target compositions) andtherefore may require different energies, pressures, etc. to be createdand maintained. As well, the magnets of the cathodes may be configuredin various ways to shape the plasmas and create varying densitiesappropriate for a particular deposition profile for a desired ECelement. As depicted in FIG. 4M, this configuration creates three zones.Zone 1 is a material deposition zone that is substantially comprised ofthe material from which target 1 is made. Zone 3 is a materialdeposition zone that is substantially comprised of the material fromwhich target 2 is made. Zone 2 is a material deposition zone that issubstantially a mixture of the two target materials. The relativeconcentrations of the plasma from target 1 and the plasma from target 2in zone 2 is generally a gradient along the length (parallel totranslation of the substrate) of zone 2. The gradient can be manipulatedby, e.g., configuring the plasma densities and shapes of two successivetargets. The plasma densities, material properties, magnetic coils, andthe like are factors that allow these zones to be established andmaintained in a steady state so that varying compositions can bedeposited on the substrate as it translates past the targets.

Another parameter that affects the deposition is the speed at which thesubstrate and the target assembly pass by one another. For example, thespeed of translation of the substrate past the targets will be a factorin how much material is deposited onto the substrate. In one embodimentthe translation speed of the substrate past the targets is constant, inanother embodiment it varies. In one embodiment, the translation speedof the substrate past the targets is between about 0.1 meters per secondand about 1 meter per second, in another embodiment between about 0.1meters per second and about 0.5 meters per second, and in anotherembodiment between about 0.2 meters per second and about 0.5 meters persecond. The speed of the substrate will determine the travel distance,that is, how far a particular point on the substrate must traverse ineach deposition zone, or collectively, across the target assembly thatcreates the EC element. The thickness of the EC element, and of eachmaterial or mixture of materials deposited in each deposition zone, willdirectly depend on the translation speed, the travel distance, as wellas the plasma density, shape, etc. as described above.

FIGS. 4N and 4P depict arrangements with two rotary targets and oneplanar and one rotary target, respectively. For these configurations,the distances α and β are as described above in relation to FIG. 4M.Referring to FIG. 4N, rotary targets 1 and 2 are depicted as havingtheir internal magnets (depicted as dark curved structures in theinterior of each target) configured to generate plasmas at differentangles with respect to the substrate surface. This is another example ofhow plasma densities and shapes can be manipulated in order to creatematerial deposition zones 1-3. The rotation of the targets can be in thesame direction or not. Referring to FIG. 4P, planar target 1 and rotarytarget 2 are proximate each other. This arrangement produces anotherunique plasma deposition profile across three zones. FIGS. 4M, 4N and 4Pdepict the three possible combinations of two proximate planar and/orrotary targets. As described herein, various combinations of successiveplanar and rotary targets are possible. Considering any three successivetargets in an assembly for depositing an EC element, a planar target maybe flanked by two planar targets, two rotary targets, or one planar andone rotary target. Likewise a rotary target may be flanked by two planartargets, two rotary targets, or one planar and one rotary target. Asdiscussed above, baffles may also be used in between targets, planar orrotary, to further shape and control plasma mixing between two targets.

As described herein in relation to fabrication of an EC element,multiple targets may be arranged proximate each other and a substratepassed by the sputter plasmas emanating from the targets, includingmixing between successive targets, in order to deposit an EC element onthe substrate. One of ordinary skill in the art would appreciate thatthe more disparate the characteristics of the materials of each target,the more variables there are to be considered when configuring aparticular system to deposit an EC element, particularly creatingcontiguous plasmas from each target. This is true because of thedifferent power requirements, pressures, temperatures and the like thatare required for each of the target materials. In certain embodiments,the target materials are selected so that the conditions used to createplasmas from each are similar. In one embodiment, each of the assemblyof sputter targets comprises a metal oxide. In one embodiment, each ofthe assembly of sputter targets comprises a transition metal oxide. Eachtarget may also include a compound that contains a transition metal andan alkali metal, e.g., lithium tungstate. By using targets that eachhave a metal oxide, the process conditions for sputtering each of thesuccessive targets are more closely matched. This aids in sputtering anEC element, because, e.g., the pressure, temperature, power etc. aremore normalized across the targets. This allows for less complication inthe configuration of the sputter chamber that contains the targets,e.g., less baffles or other measures to accommodate pressure,temperature or power density differentials in successive target zones.For example, in one embodiment the temperature across the depositionzones does not vary by more than about 150° C., in another embodimentthe temperature across the deposition zones does not vary by more thanabout 100° C., in another embodiment the temperature across thedeposition zones does not vary by more than about 50° C. In anotherexample, the pressure across the deposition zones does not vary by morethan about 10 mTorr, in another embodiment the pressure across thedeposition zones does not vary by more than about 5 mTorr, in anotherembodiment the pressure across the deposition zones does not vary bymore than about 2 mTorr. In one embodiment an EC element is fabricatedusing a tungsten target, a lithium tungstate target and a nickeltungsten target. The EC element is fabricated using argon or other inertsputter gas along with oxygen as described herein. In one embodiment,the EC element is lithiated via lithium sputter using a lithium metaltarget downstream from the target assembly used to fabricate the ECelement.

In certain embodiments, as described above, rather than using aplurality of separate sputter targets arranged in close proximity inorder to create overlapping zones of different material plasmas, one canuse a single target with varying composition across the target (e.g. seeFIGS. 4F and/or 4G and associated description) or a plurality ofabutting targets on a single backing plate (e.g. see FIGS. 4E and/or 4Iand associated description) to fabricate an EC element. For example,taking the example from FIG. 4I, target assembly 424, where five targetsections, 470, 475, 480, 485 and 490, are affixed to a backing plate465, FIG. 4Q depicts a single plasma geometry across the five targets.In this example, the sputter target sections are abutted together orvery close together so, α, is very small or non-existent. The relativewidths of the targets are only representative, they may in reality bemuch wider or narrower than each other, depending upon the plasmadensity, amount of material desired in the deposition, thickness ofregions, etc. The distance β is shown, which is, again, important due tothe plasma densities, etc. as the substrate passes by the targetassembly. The shape and density of the plasma across the target sectionswill be affected by the magnetic field shape and strength (the blackrectangles represent the magnets of the cathode) as well as the pressureand power density used to generate the plasma. In this example, thetarget sections are of different widths and the cathode magnets arearranged asymmetrically, depending upon the desired plasma densityprofile.

In this example, since there are five target sections, nine depositionzones are established during sputter. As the leading edge of thesubstrate enters zone 1, TCO material is deposited. This deposition iscontinued until zone 2 is reached, where a graded mixture of TCO andelectrochromic material are deposited. Zone 3 is where electrochromicmaterial is deposited, followed by zone 4 where a mixture ofelectrochromic material and ion conducting material is deposited. Next,in zone 5, ion conducting material is laid down, followed by zone 6,where a mixture of ion conducting material and counter electrodematerial is deposited. In zone 7, counter electrode material isdeposited, followed by zone 8, where a mixture of counter electrodematerial and a second TCO material are deposited. Finally, in zone 9,the second TCO material is laid down.

As the substrate exits zone 9, a single layer of material, whichcomprises five functional regions, a first transparent conductingregion, an electrochromic region, an ion conducting region, a counterelectrode region and a second transparent conducting region,respectively, has been deposited on the substrate. The functionalregions may comprise any of the materials described herein for theirrespective functions. In one embodiment, the first and secondtransparent conducting regions comprise ITO, the electrochromic regioncomprises tungsten oxide, the counter electrode region comprises NiWO,and the ion conducting region comprises at least one of lithiumtungstate, silicon-aluminum-oxide lithium silicate, lithium aluminumsilicate, lithium aluminum borate, lithium aluminum fluoride, lithiumborate, lithium nitride, lithium zirconium silicate, lithium niobate,lithium borosilicate, lithium phosphosilicate and lithium phosphorousoxynitride.

The EC devices and EC elements described herein can include one or moreadditional layers or regions, respectively, such as one or more passivelayers or regions, for example to improve certain optical properties,providing moisture or scratch resistance, to hermetically seal theelectrochromic device and the like. Typically, but not necessarily, acapping layer is deposited on an EC stack or EC element. In someembodiments, the capping layer is SiAlO. In some embodiments, thecapping layer is deposited by sputtering. In one embodiment, thethickness of a capping layer is between about 30 nm and about 100 nm.

From the discussion above, it should be appreciated that EC devices andEC elements described herein can be made in a single chamber apparatus,for example a sputter tool that has, for example, a tungsten target, anickel target and a lithium target along with oxygen and argon sputtergases. As mentioned, due to the nature of the interfacial regions formedto serve the purpose of a conventional distinct IC layer, a separatetarget for sputtering an IC layer is not necessary. For example incertain embodiments, an EC and CE layer are deposited in contact witheach other and an interfacial region serving as an IC layer is formedthereafter. In other embodiments a single layer graded composition isfabricated from a target having a composition that substantiallyreflects the composition of the graded layer. Of particular interest tothe inventors is fabricating electrochromic devices and/or EC elementsdescribed herein, for example, in a high throughput fashion, thereforeit is desirable to have apparatus that can fabricate EC devices and/orEC elements sequentially as substrates pass through an integrateddeposition system. For example, the inventors are particularlyinterested in fabricating electrochromic devices on windows,particularly architectural glass scale windows (supra).

Thus, another embodiment is an apparatus for fabricating anelectrochromic device, including: an integrated deposition systemincluding: (i) a first deposition station containing a material sourceconfigured to deposit an electrochromic layer including anelectrochromic material; and (ii) a second deposition station configuredto deposit a counter electrode layer including a counter electrodematerial; and a controller containing program instructions for passingthe substrate through the first and second deposition stations in amanner that sequentially deposits a stack on the substrate, the stackhaving an intermediate layer sandwiched in between the electrochromiclayer and the counter electrode layer; where either or both of the firstdeposition station and the second deposition station are also configuredto deposit the intermediate layer over the electrochromic layer or thecounter electrode layer, and where the intermediate layer includes anoxygen rich form of the electrochromic material or the counter electrodematerial and where the first and second deposition stations areinterconnected in series and operable to pass a substrate from onestation to the next without exposing the substrate to an externalenvironment. In one embodiment, apparatus described herein are operableto pass the substrate from one station to the next without breakingvacuum and may include one or more lithiation stations operable todeposit lithium from a lithium-containing material source on one or morelayers of the electrochromic device. In one embodiment, apparatusdescribed herein are operable to deposit the electrochromic stack on anarchitectural glass substrate.

In one embodiment, the apparatus is operable to pass the substrate fromone station to the next without breaking vacuum. In another embodiment,the integrated deposition system further includes one or more lithiationstations operable to deposit lithium from a lithium-containing materialsource on at least one of the electrochromic layer, the intermediatelayer and the counter electrode layer. In yet another embodiment, theintegrated deposition system is operable to deposit the stack on anarchitectural glass substrate. In one embodiment, the apparatus isoperable to pass the substrate across a plurality of closely associatedsputter targets such that a single layer graded composition, EC element,is deposited on the substrate in a single pass. In another embodiment,the integrated deposition system further includes a substrate holder andtransport mechanism operable to hold the architectural glass substratein a vertical orientation while passing through the integrateddeposition system. In another embodiment, the apparatus further includesone or more load locks for passing the substrate between an externalenvironment and the integrated deposition system. In another embodiment,the apparatus further includes at least one slit valve operable topermit isolation of the one or more lithium deposition stations from atleast one of the first deposition station and the second depositionstation. In one embodiment, the integrated deposition system includesone or more heaters configured to heat the substrate.

FIG. 5 depicts a simplified representation of an integrated depositionsystem 500 in a perspective view and with more detail including acutaway view of the interior. In this example, system 500 is modular,where entry load lock 502 and exit load lock 504 are connected todeposition module 506. There is an entry port, 510, for loading, forexample, architectural glass substrate 525 (load lock 504 has acorresponding exit port). Substrate 525 is supported by a pallet, 520,which travels along a track, 515. In this example, pallet 520 issupported by track 515 via hanging but pallet 520 could also besupported atop a track located near the bottom of apparatus 500 or atrack, for example mid-way between top and bottom of apparatus 500.Pallet 520 can translate (as indicated by the double headed arrow)forward and/or backward through system 500. For example during lithiumdeposition, the substrate may be moved forward and backward in front ofa lithium target, 530, making multiple passes in order to achieve adesired lithiation. This function is not limited to lithium targets,however, for example a tungsten target may pass multiple times past asubstrate, or the substrate may pass by via forward/backward motion pathin front of the tungsten target to deposit, for example, anelectrochromic layer. Pallet 520 and substrate 525 are in asubstantially vertical orientation. A substantially vertical orientationis not limiting, but it may help to prevent defects because particulatematter that may be generated, for example, from agglomeration of atomsfrom sputtering, will tend to succumb to gravity and therefore notdeposit on substrate 525. Also, because architectural glass substratestend to be large, a vertical orientation of the substrate as ittraverses the stations of the integrated deposition system enablescoating of thinner glass substrates since there are fewer concerns oversag that occurs with thicker hot glass.

Target 530, in this case a cylindrical target, is oriented substantiallyparallel to and in front of the substrate surface where deposition is totake place (for convenience, other sputter means are not depicted here).Substrate 525 can translate past target 530 during deposition and/ortarget 530 can move in front of substrate 525. The movement path oftarget 530 is not limited to translation along the path of substrate525. Target 530 may rotate along an axis through its length, translatealong the path of the substrate (forward and/or backward), translatealong a path perpendicular to the path of the substrate, move in acircular path in a plane parallel to substrate 525, etc. Target 530 neednot be cylindrical, it can be planar or any shape necessary fordeposition of the desired layer with the desired properties. Also, theremay be more than one target in each deposition station and/or targetsmay move from station to station depending on the desired process. Thevarious stations of an integrated deposition system described herein maybe modular, but once connected, form a continuous system where acontrolled ambient environment is established and maintained in order toprocess substrates at the various stations within the system.

More detailed aspects of how electrochromic materials are depositedusing integrated deposition system 500 are described in U.S.Non-Provisional patent application Ser. Nos. 12/645,111 and 12/645,159,supra.

Integrated deposition system 500 also has various vacuum pumps, gasinlets, pressure sensors and the like that establish and maintain acontrolled ambient environment within the system. These components arenot shown, but rather would be appreciated by one of ordinary skill inthe art. System 500 is controlled, for example, via a computer system orother controller, represented in FIG. 5 by an LCD and keyboard, 535. Oneof ordinary skill in the art would appreciate that embodiments describedherein may employ various processes involving data stored in ortransferred through one or more computer systems. Embodiments describedherein also relate to the apparatus, such computers andmicrocontrollers, for performing these operations. These apparatus andprocesses may be employed to deposit electrochromic materials of methodsdescribed herein and apparatus designed to implement them. The controlapparatus described herein may be specially constructed for the requiredpurposes, or it may be a general-purpose computer selectively activatedor reconfigured by a computer program and/or data structure stored inthe computer. The processes presented herein are not inherently relatedto any particular computer or other apparatus. In particular, variousgeneral-purpose machines may be used with programs written in accordancewith the teachings herein, or it may be more convenient to construct amore specialized apparatus to perform and/or control the required methodand processes.

Embodiments that describe fabrication of single layer graded compositionEC elements can be made in a similar apparatus to that described inrelation to FIG. 5, with appropriate configuration of target assembliesand the like. One embodiment is an integrated deposition system forfabricating an electrochromic window, the system comprising: a pluralityof closely associated sputter targets operable to pass a substrate fromone sputter to the next without exposing the substrate to an externalenvironment, wherein the plurality of closely associated sputter targetscomprise (i) a first sputter target containing a material source fordepositing an electrochromic material; (ii) a second sputter targetcontaining a material source for depositing an ion conducting material;and (iii) a third sputter target containing a material source fordepositing a counter electrode material; and a controller containingprogram instructions for passing the substrate by the plurality ofclosely associated sputter targets in a manner that deposits on thesubstrate a single layer graded composition including: (i) anelectrochromic region, (ii) an ion conducting region, and (iii) acounter electrode region. In one embodiment, the system is operable topass the substrate past the plurality of closely associated sputtertargets without breaking vacuum. In one embodiment, the system isconfigured to deposit the single layer graded composition on anarchitectural glass substrate of at least six feet by ten feet. Inanother embodiment, the system further includes a substrate holder andtransport mechanism operable to hold the architectural glass substratein a substantially vertical orientation while in the system. The systemmay further include one or more load locks for passing the substratebetween an external environment and the integrated deposition system. Inone embodiment, the system further includes one or more lithiumdeposition stations, each comprising a lithium-containing materialsource. These stations can be used to lithiate the EC element shouldthat be desirable. In one embodiment, the system includes at least twolithium deposition stations. The system may therefore include at leastone slit valve operable to permit isolation a lithium depositionstation, apart from the plurality of closely associated sputter targets.In one embodiment, the system can be configured to accommodate a targethaving a composition that substantially reflects the composition of anEC element to be deposited. Such targets are contemplated to be wider insome instances that a traditional sputter target, depending upon thedesired thickness of the single layer graded composition film and theswitching characteristics desired.

From the description above, particularly of FIGS. 3A-3B, it can be seenthat with methods described herein, one can not only make electrochromicdevices, but also prefabricate a layered stack, for example 400, 403 and409, that can in some cases be converted through subsequent processing,for example as described herein, to an electrochromic device. Though notfunctional electrochromic devices, by virtue of not having an ionconducting and electronically-insulating region between the EC and CElayers, such “electrochromic device precursors” can be of particularvalue. This is especially true if the device precursors are manufacturedin a high purity, integrated processing apparatus as described herein,where the material layers are all deposited under a controlled ambientenvironment where, for example, vacuum is never broken. In that way,high purity, low-defect materials are stacked and essentially “sealed,”for example, by the final TCO layer and/or a capping layer prior toleaving the integrated system.

Like the electrochromic devices described above, electrochromic deviceprecursors can also include one or more additional layers (not shown)such as one or more passive layers, for example to improve certainoptical properties, providing moisture or scratch resistance, tohermetically seal the device precursor and the like. In one embodiment,a capping layer is deposited on the TCO layer of the precursor stack. Insome embodiments, the capping layer is SiAlO. In some embodiments, thecapping layer is deposited by sputtering. In one embodiment, thethickness of a capping layer is between about 30 nm and about 100 nm.Subsequent processing with the cap layer in place forms the IC layerwithout contamination from the environment, that is, with the additionalprotection of the capping layer.

Conversion of an EC device precursor to a functional electrochromicdevice can occur outside the integrated system if desired, since theinternal stack structure is protected from the outside environment andsomewhat less stringent purity conditions are necessary for the lastconditioning steps to convert the precursor stack to the functionaldevice. Such stacked electrochromic device precursors can haveadvantages, for example, longer lifespan due to conversion to theelectrochromic device only when needed, flexibility by having, forexample, a single precursor stack that can be stored and used whenconversion parameters are improved or fed to different conversionchambers and/or customer sites for conversion depending on the needs ofthe final product and quality standards that must be met. Also suchprecursor stacks are useful for testing purposes, for example, qualitycontrol or research efforts.

Accordingly, one embodiment is an electrochromic device precursorincluding: (a) a substrate; (b) a first transparent conducting oxidelayer on the substrate; (c) a stack on the first transparent conductingoxide layer, the stack including: (i) an electrochromic layer includingan electrochromic material, and (ii) a counter electrode layer includinga counter electrode material; where the stack does not include an ionconducting and electronically-insulating region between theelectrochromic layer and the counter electrode layer; and (d) a secondtransparent conducting oxide layer on top of the stack. In oneembodiment, the electrochromic layer includes tungsten oxide and thecounter electrode layer comprises nickel tungsten oxide. In oneembodiment, at least one of the stack and the electrochromic layercontain lithium. In another embodiment, the electrochromic layer istungsten oxide with superstoichiometric oxygen content at least at theinterface with the counter electrode layer. In another embodiment, thestack includes an IC precursor layer between the counter electrode layerand the electrochromic layer, the IC precursor layer including tungstenoxide with higher oxygen content than that of the electrochromic layer.In one embodiment, where there is no IC precursor layer between the ECand CE layers, the electrochromic layer is between about 500 nm andabout 600 nm thick and the counter electrode layer is between about 150nm and about 300 nm thick. In another embodiment, where there is an ICprecursor layer between the EC and CE layers, the electrochromic layeris between about 350 nm and about 400 nm thick, the IC precursor layeris between about 20 nm and about 100 nm thick, and the counter electrodelayer is between about 150 nm and about 300 nm thick. In one embodiment,precursor devices described herein are exposed to heating to convertthem to functional electrochromic devices. In one embodiment, theheating is part of an MTCC.

Another embodiment is an electrochromic device including: (a) anelectrochromic layer including an electrochromic material, and (b) acounter electrode layer including a counter electrode material, wherethe device does not contain a compositionally homogeneous layer ofelectronically-insulating, ion conducting material between theelectrochromic layer and the counter electrode layer. In one embodiment,the electrochromic material is tungsten oxide, the counter electrodematerial is nickel tungsten oxide, and between the electrochromic layerand the counter electrode layer is an interfacial region including amixture of lithium tungstate and at least one of tungsten oxide andnickel tungsten oxide. In another embodiment, the electrochromic layeris between about 300 nm and about 500 nm thick; the interfacial regionis between about 10 nm and about 150 nm thick, and the counter electrodelayer is between about 150 nm and about 300 nm thick.

EXAMPLES

FIG. 6, is a graph of a process flow used as a protocol for fabricatingelectrochromic devices. The y axis units are optical density and the xaxis units are time/process flow. In this example, an electrochromicdevice is fabricated analogous to that described in relation to FIG. 4A,where the substrate is glass with fluorinated tin oxide as the firstTCO, the EC layer is WO₃ with excess oxygen in the matrix (for example,sputtered using the tungsten target, where the sputter gas is about 60%O₂ and about 40% Ar), the CE layer is formed atop the EC layer and ismade of NiWO and the second TCO is indium tin oxide (ITO). Lithium isused as the ion source for the electrochromic transition.

Optical density is used to determine endpoints during fabrication of theelectrochromic device. Starting at the origin of the graph, opticaldensity is measured as the EC layer, WO₃, is deposited on the substrate(glass+TCO). The optical density of the glass substrate has a baselinevalue optical density of about 0.07 (absorbance units). The opticaldensity increases from that point as the EC layer builds, becausetungsten oxide, although substantially transparent, absorbs some visiblelight. For a desired thickness of the tungsten oxide layer about 550 nmthick, as described above, the optical density rises to about 0.2. Afterdeposition of the tungsten oxide EC layer, lithium is sputtered on theEC layer as indicated by the first time period denoted “Li.” During thisperiod, the optical density increases along a curve further to about0.4, indicating that the blind charge of the tungsten oxide has beensatisfied, as tungsten oxide colors as lithium is added. The time perioddenoted “NiWO” indicates deposition of the NiWO layer, during which theoptical density increases because NiWO is colored. The optical densityincreases further during NiWO deposition from about 0.4 to about 0.9 forthe addition of a NiWO layer about 230 nm thick. Note that some lithiummay diffuse from the EC layer to the CE layer as the NiWO is deposited.This serves to maintain the optical density at a relatively lower valueduring the NiWO deposition, or at least during the initial phase of thedeposition.

The second time period denoted “Li” indicates addition of lithium to theNiWO EC layer. The optical density decreases from about 0.9 to about 0.4during this phase because lithiation of the NiWO bleaches the NiWO.Lithiation is carried out until the NiWO is bleached, including a localminima at about 0.4 optical density. The optical density bottoms out atabout 0.4 because the WO₃ layer is still lithiated and accounts for theoptical density. Next, as indicated by time period “extra Li” additionallithium is sputtered onto the NiWO layer, in this example about 10%additional lithium as compared to that added to the NiWO to bleach it.During this phase the optical density increases slightly. Next theindium tin oxide TCO is added, as indicated by “ITO” in the graph.Again, the optical density continues to rise slightly during formationof the indium tin oxide layer, to about 0.6. Next, as indicated by timeperiod denoted “MSTCC” the device is heated to about 250° C., for about15 minutes under Ar, and then about 5 minutes under O₂. Then the deviceis annealed in air at about 300° C. for about 30 minutes. During thistime, the optical density decreases to about 0.4. Thus optical densityis a useful tool for fabricating devices, for example for determininglayer thickness based on material deposited and morphology, andespecially for titrating lithium onto the various layers for satisfyingblind charge and/or reaching a bleached state.

FIG. 7 shows a cross section TEM of an electrochromic device 700fabricated using methods described herein, consistent with the protocolas described in relation to FIG. 6. Device 700 has a glass substrate 702upon which an electrochromic stack, 714, is formed. Substrate 702 has anITO layer, 704, which serves as the first TCO. A tungsten oxide EClayer, 706, is deposited on TCO 704. Layer 706 was formed at a thicknessof about 550 nm, that is, WO₃ formed via sputtering tungsten with oxygenand argon as described above in relation to FIG. 6. To the EC layer wasadded lithium. Then a CE layer, 710, of NiWO, about 230 nm thick, wasadded followed by addition of lithium to bleach and then about 10%excess. Finally an indium tin oxide layer, 712, was deposited and thestack was subjected to multistep thermochemical conditioning asdescribed above in relation to FIG. 4A. After the MSTCC, this TEM wastaken. As seen, a new region, 708, which is ion conductingelectronically-insulating, was formed.

FIG. 7 also shows five selected area electron diffraction (SAED)patterns for the various layers. First, 704 a, indicates that the ITOlayer is highly crystalline. Pattern 706 a shows that the EC layer ispolycrystalline. Pattern 708 a shows that the IC layer is substantiallyamorphous. Pattern 710 a shows that the CE layer is polycrystalline.Finally, pattern 712 a shows that the indium tin oxide TCO layer ishighly crystalline.

FIG. 8 is a cross section of a device, 800, analyzed by scanningtransmission electron microscopy (STEM). In this example, device 800 wasfabricated using methods described herein, consistent with the protocolas described in relation to FIG. 4B. Device 800 is an electrochromicstack formed on a glass substrate (not labeled). On the glass substrateis a fluorinated tin oxide layer, 804, which serves as the first TCO(sometimes called a “TEC” layer, for transparent electronic conductor”).A tungsten oxide EC layer, 806, was deposited on TCO 804. In thisexample, layer 806 was formed at a thickness of about 400 nm, that is,WO₃ formed via sputtering tungsten with oxygen and argon as describedabove in relation to FIG. 6, then an oxygen rich precursor layer, 805,was deposited to a thickness of about 150 nm. To layer 805 was addedlithium. Then a CE layer, 810, of NiWO, about 230 nm thick, was addedfollowed by addition of lithium to bleach and then about 10% excess.Finally an indium tin oxide layer, 812, was deposited and the stack wassubjected to multistep thermochemical conditioning as described above inrelation to FIG. 4B. After the MSTCC, this STEM was taken. As seen, anew region, 808, which is ion conducting electronically-insulating, wasformed. The difference between this example and the embodiment describedin relation to FIG. 4B, is that here the oxygen rich layer 805, unlikeanalogous layer 405 in FIG. 4B, was only partially converted to theinterfacial region 808. In this case only about 40 nm of the 150 nm ofoxygen rich precursor layer 405 was converted to the region serving asthe ion conducting layer.

FIGS. 8B and 8C show a “before and after” comparison of device, 800,(FIG. 8C) and the device precursor (FIG. 8B) before multistepthermochemical conditioning as analyzed by STEM. In this example, onlylayers 804-810, EC through CE, are depicted. The layers are numbered thesame as in FIG. 8A, with a few exceptions. The dotted line in FIG. 8B isused to approximately demark the interface of EC layer 806 and oxygenrich layer 805 (this is more apparent in FIG. 8C). Referring again toFIG. 8B, it appears that at least there is lithium, as indicated by 808a, concentrated (approximately 10-15 nm thick region) at the interfaceof oxygen rich layer 805 and CE layer 810. After MTCC, FIG. 8C, it isclear that interfacial region 808 has formed.

Although the foregoing has been described in some detail to facilitateunderstanding, the described embodiments are to be consideredillustrative and not limiting. It will be apparent to one of ordinaryskill in the art that certain changes and modifications can be practicedwithin the scope of the appended claims.

What is claimed is:
 1. An EC element comprising a single layer gradedcomposition comprising an EC region, an IC region and a CE region,respectively.
 2. The EC element of claim 1 which is all solid-state andinorganic.
 3. The EC element of claim 2, comprising: a) a firsttransition metal and a second transition metal, wherein the EC regioncomprises the first transition metal and optionally comprises the secondtransition metal, wherein the EC region composition comprises a highermole fraction of the first transition metal compared to the secondtransition metal; b) an alkali metal having a maximum mole fraction ofthe composition in the IC region as compared to the EC region and the CEregion; and c) the second transition metal having its maximum molefraction, of the composition of any region of the EC element, in the CEregion.
 4. The EC element of claim 2, comprising: a) a first transitionmetal having a maximum concentration, relative to other metals in the ECelement, in the EC region; b) an alkali metal having a maximumconcentration, relative to other metals in the EC element, in the ICregion; and c) a second transition metal having its absolute maximumconcentration in the CE region of the EC element.
 5. The EC element ofclaim 3 or 4, further comprising oxygen in each of the EC, IC and CEregions.
 6. The EC element of claim 2, comprising: a) a first transitionmetal oxide which is the primary constituent of the EC region; b) amixed transition metal oxide which is the primary constituent of the CEregion; and c) a mixture comprising an alkali metal-containing compound,the first transition metal and the mixed transition metal oxide, saidmixture the primary constituent of the IC region.
 7. The EC element ofclaim 6, wherein the mixed transition metal oxide comprises the firsttransition metal and a second transition metal selected from the groupconsisting of nickel, tantalum, titanium, vanadium, chromium, cerium,cobalt, copper, iridium, iron, manganese, molybdenum, niobium,palladium, praseodymium, rhodium and ruthenium.
 8. The EC element of anyone of claims 3-7, wherein the first transition metal is tungsten andthe alkali metal is lithium.
 9. The EC element of claim 8, wherein thesecond transition metal is nickel.
 10. The EC element of any one ofclaims 3-7, wherein the EC region is cathodically coloring and the CEregion is anodically coloring.
 11. The EC element of claim 10,configured to operate by migration of lithium ions from the CE region,through the IC region and into the EC region, or, from the EC region,through the IC region and into the CE region, when a potential isapplied across the EC element.
 12. The EC element of claim 6, whereinthe first transition metal oxide is tungsten oxide and the mixedtransition metal oxide is nickel tungsten oxide.
 13. An EC devicecomprising: a) a first transparent electrode; b) a second transparentelectrode; and c) the EC element of any one of claims 1-7, 9, 11-12sandwiched therebetween.
 14. The EC device of claim 13, wherein thefirst and second transparent electrodes comprise tin oxide basedmaterials.
 15. The EC device of claim 14, fabricated on a glasssubstrate.
 16. The EC device of claim 15, further comprising a diffusionbarrier between the glass substrate and the EC device.
 17. An EC elementwhich is a single layer graded composition comprising: d) an EC regioncomprising primarily tungsten oxide; e) a CE region comprising primarilynickel tungsten oxide; and, therebetween, f) an IC region comprising amixture of lithium tungstate, tungsten oxide and nickel tungsten oxide.18. An EC device comprising the EC element of claim
 17. 19. The ECdevice of claim 18, wherein the EC element is sandwiched between twotransparent conductive electrodes.
 20. An EC element which is a singlelayer graded composition comprising: a) An EC region comprising atungsten oxide rich matrix which transitions to a matrix withincreasingly more lithium tungstate; b) an IC region comprising amixture of lithium tungstate, tungsten oxide and nickel tungsten oxide,the IC region transitioning, moving away from the EC region: i. frommore to less tungsten oxide; ii. from less to more nickel tungstenoxide; and iii. having a lithium tungstate rich matrix near a centralportion of the IC region; and c) a CE region which transitions, movingaway from the IC region, from more to less lithium tungstate to a nickeltungsten oxide rich matrix.
 21. An EC device comprising the EC elementof claim
 20. 22. The EC device of claim 20, wherein the EC element issandwiched between two transparent conductive electrodes.
 23. The ECelement of any one of claims 3-7, 17 and 20, further comprising,abutting one of the EC or the CE face of the EC element, a reflectivecoating, a thermochromic coating or a photochromic coating.
 24. An ECdevice comprising the EC element of claim 23 sandwiched between twotransparent conductive electrodes.
 25. The EC device of claim 24,comprising a reflective coating abutting the CE face of the EC element.26. The EC device of claim 25, configured to operate by migration oflithium ions from the CE region, through the IC region and into the ECregion, or, from the EC region, through the IC region and into the CEregion, when a potential is applied across the EC element.
 27. The ECelement or device of any of claim 1, 17, or 20, wherein an interfacebetween the EC region and the IC region or between the IC region and theCE region has a composition gradient of at least about 20 nm.
 28. The ECelement or device of any of claim 1, 17, or 20, wherein an interfacebetween the EC region and the IC region or between the IC region and theCE region has a composition gradient of at least about 5% of the totalelement thickness of the EC element.